UNIVERSITY  OF  CALIFORNIA  PUBLICATIONS 


COLLEGE  OF  AGRICULTURE 

AGRICULTURAL  EXPERIMENT  STATION 

BERKELEY,  CALIFORNIA 


THE  RED  OR  ORANGE  SCALE 

By  H.  J.  QUAYLE 


BULLETIN  No.  222 

(Berkeley,  Cal.,  July,  1911) 


W.  YV.  Shannon 


SACRAMENTO 

-     -     Superintendent  of  State  Printing 
1911 


Benjamin  Ide  Wheeler,  President  of  the  University. 

EXPERIMENT  STATION  STAFF. 

E.  J.  Wickson,  M.A.,  Director  and  Horticulturist. 

E.  W.  Hilgard,  Ph.D.,  LL.D.,  Chemist   (Emeritus). 

W.  A.  Setchell,  Ph.D.,  Botanist. 

Leroy  Anderson,  Ph.D.,  Dairy  Industry  and  Superintendent  University  Farm  Schools 

M.  E.  Jaffa,  M.S.,  Nutrition  Expert. 

R.  H.  Loughridge,  Ph.D.,  Soil  Chemist  and  Physicist  (Emeritus). 

C.  W.  Wood  worth,  M.S.,  Entomologist. 

Ralph  E.   Smith,  B.S.,  Plant  Pathologist  and  Superintendent  of  Southern   California 

Pathological  Laboratory  and  Experiment  Station. 
G.  W.  Shaw,  M.A.,  Ph.D.,  Experimental  Agronomist  and  Agricultural  Technologist,  in 

charge  of  Cereal  Stations. 

E.  W.  Major,  B.Agr.,  Animal  Industry. 

B.  A.  Etcheverry,  B.S.,   Irrigation  Expert. 

F.  T.   Bioletti,  B.S.,  Viticulturist. 

W.  T.  Clarke,  B.S.,  Assistant  Horticulturist  and  Superintendent  of  University  Exten- 
sion  in  Agriculture. 

John  S.  Burd,  B.S.,  Chemist,  in  charge  of  Fertilizer  Control. 

J.  E.  Coit,  Ph.D.,  Assistant  Pomologist,  Plant  Disease  Laboratory,  Whittier. 

George  E.  Colby,  M.S.,  Chemist  (Fruits,  Waters,  and  Insecticides),  in  charge  of 
Chemical  Laboratory. 

H.  J.  Quayle,  M.S.,  Assistant  Entomologist,  Plant  Disease  Laboratory,  Whittier. 

H.  M.  Hall,  Ph.D.,  Assistant  Botanist. 

C.  M.  Haring,  D.V.M.,  Assistant  Veterinarian  and  Bacteriologist. 
E.  B.  Babcock,  B.S.,  Assistant  Agricultural  Education. 

W.  B.  Herms,  M.A.,  Assistant  Entomologist. 

J.  H.  Norton,  M.S.,  Assistant  Chemist,  in  charge  of  Citrus  Experiment  Station,  River- 
side. 
W.  T.  Horne,  B.S.,  Assistant  Plant  Pathologist. 
C.  B.  Lipman,  Ph.D.,   Soil  Chemist  and  Bacteriologist. 
R.  E.  Mansell,  Assistant  Horticulturist,  in  charge  of  Central  Station  grounds. 

A.  J.  Gaumnitz,  Assistant  Agronomist,  University  Farm,  Davis. 
N.  D.  Ingham,  B.S.,  Assistant  in  Sylviculture,  Santa  Monica. 

T.  F.  Hunt,  B.S.,  Assistant  Plant  Pathologist. 

P.  L.  McCreary,  B.S.,  Chemist  in  Fertilizer  Control. 

E.  H.  Hagemann,  Assistant  in  Dairying,  Davis. 

R.  M.  Roberts,  Farm  Manager,  University  Farm,  Davis. 

B.  S.  Brown,  B.S.A.,  Assistant  Horticulturist,  University  Farm,  Davis. 
J.  I.  Thompson,  B.S.,  Assistant  Animal  Industry,  Davis. 

Howard  Phillips,  B.S.,  Assistant  Animal  Industry,  Davis. 
J.  C.  Bridwell,  B.S.,  Assistant  Entomologist. 

C.  H.  McCharles,  M.S.,  Assistant  Agricultural  Chemical  Laboratory. 

E.  H.  Smith,  M.S.,  Assistant  Plant  Pathologist. 

C.  O.  Smith,  M.S.,  Assistant  Plant  Pathologist,  Plant  Disease  Laboratory,  Whittier. 

F.  E.  Johnson,  B.L.,  M.S.,  Assistant  Soil  Chemist. 

B.  A.  Madson,  B.S.A.,  Assistant  Experimental  Agronomist. 

Walter  E.  Packard,  M.S.,  Field  Assistant  Imperial  Valley  Investigation,  El  Centro. 

P.  L.  Hibbard,  B.S.,  Assistant  Fertilizer  Control  Laboratory. 

L.  M.  Davis,  B.S.,  Assistant  in  Dairy  Husbandry,  University  Farm,  Davis. 

S.  S.  Rogers,  B.S.,  Assistant  Plant  Pathologist,  Plant  Disease  Laboratory,  Whittier. 

L.  Bonnet,  Assistant  Viticulturist. 

H.  A.  Ruehe,  B.S.A.,  Assistant  in  Dairy  Husbandry,  University  Farm,  Davis. 

F.  C.  H.  Flossfeder,  Assistant  in  Viticulture,  University  Farm,  Davis. 

S.  D.  Wilkins,  Assistant  in  Poultry  Husbandry,  University  Farm,  Davis. 

C.  L.  Roadhouse,  D.V.M.,  Assistant  in  Veterinary  Science. 
F.  M.  Hayes,  D.V.M.,  Assistant  Veterinarian. 

F.  L.  Yeaw,  B.S.,  Assistant  Plant  Pathologist,  University  Farm,  Davis. 
M.  E.  Stover,  B.S.,  Assistant  in  Agricultural  Chemical  Laboratory. 

W.  H.  Volck,  Field  Assistant  in  Entomology,  Watsonville. 

E.  L.  Morris,  Field  Assistant  in  Entomology,  San  Jose. 

E.  E.  Thomas,  B.S.,  Assistant  Chemist,  Plant  Disease  Laboratory,  Whittier. 

A.  B.  Shaw,  B.S.,  Assistant  in  Entomology. 

G.  P.  Gray,  M.S.,  Chemist  in  Insecticides. 

H.    D.   Young,  B.S.,   Assistant   in  Agricultural   Chemistry,    Plant  Disease   Laboratory, 

Whittier. 
A.  R.  Tylor,  B.S.,  Assistant  in  Plant  Pathology,  Plant  Disease  Laboratory,  Whittier. 
E.  W.  Rust,  A.B.,  Assistant  in  Entomology,  Plant  Disease  Laboratory,  Whittier. 
L.  T.  Sharp,  B.S.,  Assistant  in  Soils. 
W.  W.  Cruess,  B.S.,  Assistant  in  Zymology. 
J.  F.  Mitchell,  D.V.M.,  Assistant  in  Veterinary  Laboratory. 
J.  C.  Roper,  Patron,  University  Forestry  Station,  Chico. 
E.  C.  Miller,  Foreman,  Forestry  Station,  Chico. 

D.  L.  Bunnell,  Secretary  to  Director. 


CONTENTS. 


Page:. 

HISTORICAL 99 

DISTRIBUTION   101 

ECONOMIC   IMPORTANCE   102 

FOOD  PLANTS 1 105 

DESCRIPTION  OF  THE  STAGES 106 

First  Larvae  Stage 100 

Second  Stage  Female 106 

The  Adult  Female 107 

The  Second  Stage  Male 107 

The  Male  Propupa 108 

The  Male  Pupa 108 

The  Adult  Male 108 

LIFE  HISTORY  AND  HABITS 109 

The  Active  Larva 109 

Settling  of  the  Larvae 110 

Formation  of  the  Scale  Covering 111 

The  Fixed  Young 114 

Molting    114 

The  Adult  Male 417 

The  Adult  Female 118 

Length  of  Adult  Life 118 

Age  at  Which  Young  are  Produced 110 

Aspidiotus  aurantii — Development 120 

Embryonic  Development 121 

Parthenogenesis , 121 

Emergence  of  Young 121 

Do  the  Insects  Move  After  Becoming  Fixed i 125 

SEASONAL  HISTORY 126 

Annual  Progeny 126 

Mortality   127 

LOCOMOTION   AND    SPREAD   127 

Rate  of  Travel  Over  Smooth  Surface 129 

Rate  of  Travel  Over  Sand  and  Orchard  Soil '  130 

The  Wind 131 

PARASITES 131 

Aphelinus  Diaspidis  How. 131 

Economic  Value = 132 

Description  of  the   Stages 132 

Life  History  and  Habits 133 

Key  to  the  Species  Recorded  from  C.  aurantii 136 

Prospaltella  aurantii  How. 136 

COCCOPHAGUS  LUNULATUS  HOW. 136 

Aspidiotiphagus  citrinus  Craw. 1* JT 

skinipiiora  occidentalis  how. 137 

Aphycus  immaculatus  How. 138 

Alaptus  eriococci  Girault 13s 


1 V  CONTENTS. 

Page. 

PREDATORY  ENEMIES 138 

Riiizobius  lophantii^:  Blaisd. 138 

The  Eggs .139 

The  Mature  Larva 139 

The  Adult 140 

Orcus  ciialybeus  Boisd. 141 

Other  Enemies 141 

THE  YELLOW  SCALE  (Crysomphalus  aurantii  var.  citrinus  Coq.) 141 

Economic  Importance 142 

Difference  Between  the  Red  and  Yellow  Scales 144 

Parasites 145 

Aspidiotiphagus  citrinus  Craw. 145 

The  Egg 146 

The  Mature  Larva 146 

The  Pupa 146 

The  Adult 146 

SYSTEMATIC  POSITION  OF  CHRYSOMPHALUS  AURANTII  Mask.___  148 

BIBLIOGRAPHY    149 


THE  RED  OR  ORANGE  SCALE. 

Chrysomphalus  aurantii  Mask. 
By  H.  J.  Quayle. 

HISTORICAL. 

Chrysomphalus  aurantii  was  first  described  from  New  Zealand  by 
W.  M.  Maskell  in  1878.  The  specimens  described  were  found  infesting 
oranges  and  lemons  imported  into  New  Zealand  from  Sydney.  Two 
years  later  Professor  Comstock  observed  a  scale  infesting  orange  groves 
at  San  Gabriel  and  Los  Angeles,  California.  At  first  these  were 
described  by  Comstock  as  a  new  species,  but  after  receiving  copies  of 
Maskell 's  papers,  giving  the  description  of  Chrysomphalus  aurantif,  and 
upon  receiving  specimens  from  New  Zealand,  he  concluded  that  they 
were  the  same  as  those  occurring  there. 

Regarding  the  occurrence  of  the  scale  in  this  state  in  1880  Comstock 
says,  "I  have  observed  this  species  in  several  groves  at  San  Gabriel  and 
Los  Angeles.  At  the  first  named  place,  where  it  is  very  abundant,  it  is 
said  to  have  first  appeared  on  a  budded  orange  tree  which  was  purchased 
by  Mr.  L.  J.  Rose,  at  one  of  the  hothouses  in  San  Francisco.  At  Los 
Angeles  it  appears  to  have  spread  from  six  lemon  trees  which  were 
brought  from  Australia  by  Don  Mateo  Keller.  Thus  the  question  as  to 
the  source  from  which  we  derived  this  pest  is  settled  beyond  a  doubt." 

While  it  is  undoubtedly  true  that  this  scale  was  imported  into  this 
state  directly  from  Australia,  its  native  home  can  apparently  be  traced 
further  back  than  our  acquaintance  with  it  there.  It  is  now  supposed 
that  China  is  the  native  home  of  the  red  scale,  though  this  is  not  posi- 
tively established.  The  San  Jose  scale,  Aspidiotus  perniciosus  was  sup- 
posed for  a  long  while  to  have  had  its  origin  in  Chile  or  Australia,  but 
later  investigations  showed  that  it  had  been  introduced  into  both  of  these 
countries,  and  it  was  not  until  an  exploration  was  made  of  the  Orient 
that  Marlatt1  finally  decided  that  China  is  its  native  habitat.  So  in  the 
case  of  the  red  scale,  it  appears  to  have  been  introduced  into  Australia, 
and  that  it  existed  for  centuries  before  in  some  of  the  Oriential  coun- 
tries. That  China  is  the  native  home  of  the  San  Jose  scale  is  further 
borne  out  by  its  relationships  and  distribution  as  an  insect  of  temperate 
regions.  But  in  the  case  of  the  red,  the  relationships  and  distribution 
are  that  of  a  tropical  or  semi-tropical  insect  rather  than  one  of  tem- 
perate regions. 

Maskell  N.  Z.  Trans.  XI,  p.   199    (1878). 

Can.  Ent.  XIII,  p.   8   (1881). 

U.   S.  D.  A.  Rep.,  p.   294    (1880). 

iMarlatt  Bulletin  62,  Bur.  Ent.  U.  S.  D.  A.,  p.  10  (1906). 


100 


UNIVERSITY  OF  CALIFORNIA EXPERIMENT  STATION. 


Bulletin  222] 


THE   RED   OR   ORANGE   SCALE. 


101 


DISTRIBUTION. 
Over  World.  The  red  or  orange  scale  is  very  widely  distributed  over 
the  world,  as  shown  by  the  accompanying  map.  It  will  be  noticed  that 
it  is  largely  a  tropical  or  semi-tropical  insect.  New  Zealand  represents 
the  most  southern  location  with  a  south  latitude  of  45°  and  New  York 
the  most  northern  point  with  a  latitude  of  45°  north.  But  the  red  scale 
is  not  a  pest  in  New  York,  and  we  are  not  sure  but  that  this  is  simply  a 
greenhouse  or  incidental  locality.  While  it  occurs  in  New  Zealand  at  a 
latitude  of  45°  south  there  is  here  really  a  semi-tropical  climate,  for 


"j r i 

vi                                i 

i       /  \         i             i       . 

;  v^     f         ■ '  j j 

C 

/   _ .. J — , 

__.i — \             s*\           \  i 

\       u-.-t-y  \    .     )\ 

)       h      V  y^Z  "i 

{ {\:t&Si 

v —  v    h      \\      '             •/\ 

V*   -■ajni    _  //""'  F          /'             *-.         \ 

M     \v-SssiV]          v     /                \        \ 

^jt>v, -•'  T     ,  -!  X,  r y~  VJ          \ 

VNV.                i    '                    ''    >S-                           '                     V                               'X 

■v     -^v,          y        ^           y         ^jj-                v-                   . 

\   '*■_             \.y                   >''                          \ 

\ 

\ 

\. 

)  \       \/                                     _. ( 

s. 
\ 

\ 

N 

■^.       i 

T                                            v                  , 

Vt 

'■                                                  x           ( 

\      L 

>               1_ 

!                                           \  ? 

i                    K 

Co*        I            \ 

^"^"S.o*     \       0* 

./'    o* 

>^'^  ,. 

/     /-— i    i 

VJ~"i 

x°* 

Lo+          ; 

Fig.  2. — Map  indicating  distribution  of  Red  and  Yellow  Scales  in  principal 
citrus  fruit  areas  of  California,  o  represents  C.  aurantii;  x  represents 
C.  aurantii  var.   citrinus. 

citrus  trees  are  grown.  According  to  Dewar1,  this  scale  is  the  most 
important  citrus  fruit  pest  in  the  Orange  River  Colony.  In  West 
Australia  it  is  also  considered  the  most  serious  scale  of  citrus  trees.  It 
also  occurs  as  a  citrus  pest  in  Cape  Colony  and  other  localities  where 
citrus  fruits  are  grown. 

'Ann.  Rep.  E!nt.  Orange  River  Colony. 


102 


UNIVERSITY   OP   CALIFORNIA — EXPERIMENT   STATION 


The  following  places  are  recorded  as  having  the  red  scale :  Mauritius, 
Ceylon,  India,  S.  Europe,  Syria,  Natal,  Cape  Colony,  China,  Japan, 
Australia,  New  Zealand,  Java,  New  Caledonia,  Samoa,  Fiji,  West  Indies, 
Greece,  Turkey,  Italy,  Spain,  Singapore,  New  York,  Ohio,  Florida,  and 
California. 

In  California.  While  the  red  scale  is  recorded  from  many  other  food 
plants  than  citrus  trees,  in  this  state  it  is  limited  as  a  pest  entirely  to  the 
citrus,  so  that  its  distribution  is  governed  largely  by  this  host  plant.  In 
the  citrus  area  south  of  the  Tehachapi,  this  scale  occurs  in  the  following 
counties :  Santa  Barbara,  Ventura,  Orange,  Los  Angeles,  Riverside,  San 


5  A  N 
BERNARDINO 


**'*1fe«£i^- 


.^Corona 
r*y   /jSarxfa.Ana 

gCf     /   RIVERSIDE 


SAN 
0  I  EGO 


Fig.  3. — Map  showing  distribution  of  Red  Scale  over  southern  California 

citrus  belt. 

Bernardino,  and  San  Diego.  In  Tulare  County  it  occurs  on  citrus  trees 
in  the  city  of  Visalia,  but  has  not  yet  reached  the  commercial  citrus 
section  of  that  county  around  Porterville,  Lindsay,  and  Exeter.  It  has 
been  noted  in  abundance  on  orange  and  ivy  at  Selma  in  the  San  Joaquin 
Valley.  It  does  not  occur,  so  far  as  known,  in  Butte  County,  the  citrus 
section  of  the  Sacramento  Valley.  Here  its  place  is  occupied  by  the 
variety  citrinus. 


ECONOMIC  IMPORTANCE. 

The  red  scale  is  the  second  most  important  insect  enemy  of  citrus 
trees  in  California.  In  fact,  a  good  deal  of  evidence  may  be  submitted 
for  its  claim  to  first  place.    If  the  yellow  is  included,  which  is  justifiable, 


Bulletin  222 J 


THE  RED   OR   ORANGE   SCALE. 


103 


since  it  is  only  a  variety  of  the  red,  the  total  amount  of  control  work 
directed  against  these  would  nearly,  if  not  quite,  equal  that  against  its 
competitor  for  first  place,  the  Mack  scale.  The  black  is  more  generally 
distributed,  and  has  first  place  in  most,  if  not  all,  of  the  coast  counties. 
In  the  case  of  other  scales  occurring  with  the  black,  the  black  is  usually 
considered  as  the  least  important  when  it  comes  to  fumigating,  since  they 
are,  if  in  the  proper  stage,  more  readily  killed.     For  this  reason  the 


Fig.   4. — Tree  partially  killed  by  Red  Scale. 

black  is  sunk  into  second  place,  whereas,  if  left  untreated,  would  prob- 
ably cause  more  injury  than  the  one  which  the  treatment  was  especially 
directed  against. 

The  red  scale  ranks  first  as  a  citrus  pest  in  Riverside  and  San  Ber- 
nardino counties,  two  of  the  great  citrus  producing  counties  of  the  state. 
It  also  holds  second  place  in  Los  Angeles  and  Orange  counties,  two  other 


104 


UNIVERSITY   OF   CALIFORNIA EXPERIMENT   STATION. 


counties  where  the  citrus  industry  is  of  first  importance.  In  San  Ber- 
nardino County  about  $200,000  is  spent  annually  for  fumigation  and 
$10,000  more  for  spraying  to  control  citrus  fruit  pests.  In  Riverside 
County  $75,000  is  spent  annually  in  fumigation  and  $8,000  in  spraying 
for  the  same  pests.  While  all  of  this  is  not  directed  against  the  red  scale, 
the  majority  of  it  is,  since  in  these  two  counties  the  red  is  the  most 
injurious  pest. 


Fig.  5. — 1  Red  Scale  on  lemon.     2  Red  Scale  on  nightshade.     3  Red  Scale 
on  twig  of  lemon. 

No  citrus  scale  in  California  so  quickly  and  so  permanently  injures 
the  tree  as  the  red  scale.  The  black  seldom,  if  ever,  kills  a  tree,  its  chief 
injury  being  due  to  the  sooty  mold  fungus  on  the  fruit.  The  purple 
often  kills  but  a  few  of  the  lower  or  interior  branches.  But  practically 
the  entire  tree  may  be  killed  by  the  red,  sometimes  in  one  or  two  years ' 
infestation.  It  infests  all  parts  of  the  tree,  leaves,  branches,  fruit.  It 
not  only  causes  a  dropping  of  the  leaves,  but  actually  kills  large 
branches.  Aside  from  this  permanent  and  serious  injury  to  the  tree, 
the  presence  of  the  scale  on  the  fruit  renders  it  unmarketable.  Trees 
that  do  not  have  a  severe  infestation  of  the  scale,  and  where  the  tree 
itself  is  not  seriously  injured,  may  have  its  fruit  badly  infested  by  the 
scale. 


Bulletin  222]  THE  RED  OR  ORANGE  SCzYLE.  105 

No  honey  dew  is  given  off  by  the  red  scale,  so  that  the  characteristic 
injury  by  the  sooty  mold  fungus,  as  occurs  with  the  unarmored  scales, 
is  not  present  in  the  case  of  the  red.  The  injury  is  due  directly  to  the 
feeding  of  the  scales  themselves,  and,  aside  from  their  feeding,  the  fruit 
is  marred  simply  by  their  presence. 

The  injury  by  feeding  is  due  to  the  loss  of  chlorophyl,  toxic  effect  on 
the  tissues  of  the  plant,  and  interference  with  the  functions  of  the 
stomata  when  the  scale  is  abundant.  Some  scales  have  a  much  more 
virulent  poisoning  effect  on  the  tissues  than  others.  One  of  the  most 
marked  in  this  respect  is  the  San  Jose  scale  Aspidiotus  pemiciosus 
Comst.  On  the  fruit  of  apple  or  pear  it  causes  a  distinct  reddening  of 
the  surface  tissue.  If  the  bark  be  cut  off  where  this  insect  is  present 
the  deeper  tissues  will  be  seen  to  have  a  blackish  red  color.  With  such 
insects  the  presence  of  a  few  will  noticeably  injure  the  tree.  In  the  case 
of  others,  such  as  the  Greedy  scale,  Aspidiotus  rapax  Comst.,  the  tree 
may  be  completely  incrusted  with  them,  yet  the  tree  suffers  no  noticeable 
injury.  It  is  only  necessary  to  notice  infestations  of  this  scale  on  acacia, 
laurel  and  others  to  see  how  abundant  they  may  become  and  still  the 
tree  appears  normal.  There  is,  to  be  sure,  some  injury  done  here,  but 
it  must  be  largely  on  account  of  loss  of  sap,  and  where  the  tree  has  plenty 
•of  moisture  it  can  withstand  a  considerable  drain  in  this  respect.  If  the 
same  number  of  San  Jose  scales  were  to  infest  a  tree  as  often  occurs  with 
the  rapax  on  acacia,  laurel  and  others,  the  tree  would  be  entirely  killed. 
So  with  the  red  on  the  orange,  a  heavy  infestation  on  the  twigs  and 
branches,  as  well  as  on  the  leaves  and  fruit,  means  the  destruction  of  the 
tree. 

FOOD  PLANTS. 

While  the  list  of  food  plants  of  the  red  or  orange  scale  is  large,  it  is 
restricted  very  largely  as  a  pest,  to  citrus  trees.  It  is  recorded  from  a 
number  of  deciduous  fruit  trees,  but  is  not  a  serious  pest  on  those  trees. 
Most  of  the  other  food  plants  are  ornamental,  and  pests  on  such  plants 
never  rank  in  importance  with  those  on  commercial  fruit  trees.  Here 
in  California  the  red  scale  is  practically  unknown  away  from  the  orange 
or  lemon.  It  does,  of  course,  get  on  to  several  different  kinds  of  plants, 
but  from  an  economic  standpoint  it  is  of  little  consequence  excepting  on 
the  citrus.  It  frequently  happens  that  other  trees,  near  by  citrus  trees 
badly  infested  with  this  scale,  will  be  infested  to  a  greater  or  less  degree ; 
but  it  is  not  often  that  such  trees  or  plants  are  permanently  infested, 
and  they  seldom  become  serious  enough  to  warrant  treatment.  The 
problem  of  controlling  the  red  scale,  then,  is  limited  practically  to  citrus 
trees.  In  this  respect  the  black  scale  presents  a  different  situation. 
Outside  the  citrus  groves,  three  very  important  host  plants,  olive,  ole- 


106 


UNIVERSITY'   OF   CALIFORNIA EXPERIMENT   STATION. 


ander,  and  pepper  occur  abundantly  and  everywhere  in  southern 
California.  One  of  the  food  plants,  aside  from  the  citrus,  that  is  import- 
ant from  a  control  standpoint  is  the  nightshade  Solarium  douglassii. 
This  weed  occurs  in  waste  places  and  also  among  the  trees  in  the  grove ; 
but  the  presence  of  this  plant  in  a  grove  usually  means  neglect  in 
cultivation  or  care  of  the  trees.  These  plants,  growing  as  they  do  under 
and  among  the  trees,  may  be  a  source  of  reinfestation  after  fumigation. 
The  castor  bean  is  another  common  native  plant  attacked,  but  it  is  not 
generally  in  such  close  proximity  to  citrus  trees. 

The  complete  list  of  food  plants  from  which  the  red  scale  has  been 
recorded  is  as  follows :  orange,  lemon,  cocoanut,  fig,  olive,  agave,  plum, 
lignum  vita?,  buxus,  Euonymus,  Pistacia,  rose,  pear,  quince,  apple, 
willow,  oak,  grape,  acacia,  tea  plant,  Podocarpus,  wattle,  Ligustrumr 
Artocarpus,  sago  palm,  nightshade,  English  walnut,  eucalyptus,  cam- 
phor tree,  Kennedya,  passion  flower,  fuchsia,  Bidens,  Solidago,  date 
palm,  California  palm. 


DESCRIPTION   OF   THE   STAGES. 

First  Larval  Stage.  Length  .24  mm.  Greatest  width  .15  mm.  Color 
sulfur  yellow.  The  pygidium  has  two  central  lobes  well  developed  and 
conspicuous.    Arising  from  each  of  these  on  the  inner  and  dorsal  sides 

is  a  spine  .25  mm.  long;  also  a  small  spine 
on  outer  basal  margin.  The  median  lobes 
are  similar  in  shape  to  those  of  the  adult 
female,  that  is,  they  are  abruptly  narrowed 
at  about  one  half  their  length.  There  is  but 
a  slight  indication  of  a  second  pair  and  the 
third  is  not  present  at  all.  There  are  two 
plates  between  the  two  median  lobes  and 
also  two  between  the  first  and  second.  Be- 
yond the  second  lobe  are  from  three  to  four 
short  plates.  The  antennae  consist  of  four 
indistinct  segments  of  the  following  com- 
parative lengths  4 — 2 — 2 — 14.  The  fourth 
is  conspicuously  annulate.  There  are  six 
spines  arising  from  the  sides  of  this  segment 
and  two  at  the  extreme  tip.  The  tarsi  have 
a  single  claw,  and  there  arises  from  the  end  of  the  tibia  and  extending 
to  or  beyond  the  tip  of  the  claw  three  of  four  nobbed  hairs. 

Second  Stage  Female.  After  the  first  molt  the  scale  increases  to 
about  twice  its  original  size,  and  now  all  the  characters  of  the  pygidium 
are  distinct,  but  the  legs  and  antennae  are  lost.     There  are  three  pairs 


Fig.  6. 


-Motile  young  of  Red 
Scale.     x!75. 


Bulletin  222]  THE  RED  0H  orange  SCALE.  107 

of  conspicuous  lobes  with  a  spine  arising  from  the  base  of  each. 
Between  the  two  median  lobes  and  between  those  and  the  second  are 
two  conspicuous  plates  and  three  between  the  second  and  third  lobes. 
Beyond  this  are  three  additional  plates.  All  the  plates  are  deeply 
fringed.     There  are  no  spinnerets. 

The  Adult  Female.  The  average  dimensions  are  about  .78  mm.  wide 
and  1  mm.  long.  The  lateral  margins  of  the  body  extend  downward 
often  as  far  as  or  beyond  the  tip  of  the  pygidium. 

The  pygidium  presents  the  following  characters :  There  are  three 
pairs  of  conspicuous  lobes,  each  notched  at  about  one  half  their  length, 
making  the  distal  half  narrower  than 
the  basal.  On  the  dorsal  surface  there 
is  a  spine  accompanying  each  lobe. 
Those  of  the  first  pair  are  long  and  ( 
slender  and  situated  at  the  outer 
basal  margin,  so  placed  that  they  may 
move  either  to  the  ventral  or  dorsal 
side  of  the  lobes.  On  the  other  lobes 
there  is  one  shorter  and  more  blunt 
spine  arising  from  the  middle  of  the 
base  of  the  lobe.  On  the  ventral  sur- 
face   the    first  pair   of    lobes    have    the    fig.    7.— Ventral    view    of    Red    Scale. 

same  spines,  mentioned  above  in  con-  x50' 

nection  with  the  dorsal  surface.  On  the  other  lobes  are  each  a  single 
spine  situated  in  the  middle  at  the  base  of  the  lobe  corresponding  to 
those  above.  There  are  two  plates  between  the  first  pair  of  lobes,  two 
between  the  first  and  second,  two  between  the  second  and  third  and 
three  beyond  the  third  lobe.  The  first  plate  beyond  the  second  lobe 
and  the  three  beyond  the  third  are  deeply  bifurcated  and  fringed  on 
the  lateral  margin. 

The  dorsal  surface  of  the  pygidium  shows  a  number  of  dorsal  tubular 
spinnerets  and  several  marginal  spinnerets,  as  shown  in  the  figure.  It 
will  be  seen  from  this  that  they  are  not  arranged  uniformly  on  both  sides 
of  the  median  line.  Near  the  upper  margin  are  five  curious  shaped 
structures  with  a  couple  of  blunt  pointed  prominences  projecting 
anteriorly.  On  the  ventral  surface  the  vaginal  cleft  is  shown,  see  figure, 
with  its  radiating  lines.  The  tubular  spinnerets  may  be  faintly  seen 
from  this  surface  by  focusing  downward. 

The  Second  Stage  Male.  There  are  no  distinguishable  differences 
between  the  sexes  until  after  the  first  molt.  After  the  first  molt  the 
male  becomes  more  elongate  or  pyriform,  as  indicated  by  the  follow- 
ing measurements :  average  length  .7  mm.,  average  width  .4  mm.     The 


108 


UNIVERSITY  OF   CALIFORNIA EXPERIMENT   STATION. 


pygidium  characters  are  the  same  as  in  the  second  stage  female.  There 
are  two  pairs  of  conspicuous  purple  eyes,  one  pair  on  the  lateral  anterior 
margin,  while  the  other  pair  is  more  dorsal  and  are  nearer  together. 
Small  spines  arise  from  around  the  lateral  margin. 

The  male  propupa  is  orange  yellow  in  color  with  the  eyes  very  dark 
red  or  brown.  Length  .7  mm.,  greatest  width  .35  mm.  Dorsal  eyes  are 
just  posterior  to  antennal  sheaths  and  in  hollow  formed  by  them.  The 
ventral  eyes  are  larger  and  closer  together  and  a  little  more  posterior 
than  the  dorsal.  The  sheaths  of  the  antennas  and  wings  are  visible,  and 
a  faint  indication  of  those  of  the  legs.  But  they  are  all  more  rudi- 
mentary and  lie  closer  to  the  body  than  is  the  case  in  the  next  stage. 
There  is  no  style  present,  but  in  its  place  is  a  blunt  protuberance  from 
which  arise  two  distinct  spines.  The  truncate  posterior  end  with  the 
button  at  the  tip  is  the  most  evident  character  distinguishing  this  stage 
from  the  true  pupa. 

The  male  pupa  is  of  the  same  general  color  as  the  propupa.  Length 
exclusive  of  the  style  is  .7  mm.  The  style  is  .1  mm.  Greatest  width 
.82  mm.     The  ventral  eyes  are  large  and  almost  touching  each  other. 


Fig. 


-Stages  of  the  male  of  the  Red  Scale.     1  Second  stage.     x56. 
pupa.      x70.      3   Pupa.     x70. 


2  Pro- 


They  are  situated  a  short  distance  from  the  anterior  margin.  The  dorsal 
pair  of  eyes  are  wider  apart  and  somewhat  closer  to  the  anterior  margin. 
The  sheaths  of  the  antennas  wings  and  legs  are  evident  and  ordinarily 
lie  close  to  the  body  along  the  ventral  margin. 

The  adult  male  has  a  wing  expanse  of  1.5  mm. ;  length  exclusive  of  the 
style  .6 ;  style  .22 ;  color  orange  yellow ;  antennas  10  jointed,  the  first  two 
segments  being-  much  shorter  and  thicker  than  the  others.     The  com- 


Bulletin  222] 


THE  RED   OR   ORANGE   SCALE. 


WJ 


parative  lengths  beginning  with  the  proximal  one  are  as  follows  :  5 — 4— 

17 20 — 20 — 20—18 — 15 — 13 — 17.     Total  length  .5  mm.     The  antenna? 

are  light  colored  with  some 
yellow  pigment.  On  all  the 
joints  excepting  the  first  two 
are  rather  long  hairs.  The 
lateral  pair  of  eyes  are  dark 
brown  and  situated  just  lat- 
eral of  the  antennae.  The 
ventral  pair  of  eyes  are  much 
larger  and  closer  together  and 
situated  more  posteriorly. 
The  legs,  excepting  coxae 
which  are  yellow,  are  glassy 
white,    and    the    tarsi    light 

brown.     The  thoracic  band  is  of  a  light  brown  color.     The  halteres  are- 
club-shaped,  with  the  slender  hook  arising  from  the  tip  of  the  club. 


Male  of  Red  Scale. 


LIFE  HISTORY  AND  HABITS. 

THE   ACTIVE  LARVA. 

The  red  scale  is  viviparous,  hence  the  starting  point  in  the  life  history 
is  with  the  active  larva,  which  are  born  alive.  This  means  that  what 
ordinarily  corresponds  with  the  egg  hatches  within  the  body  of  the 
parent,  instead  of  the  embryo  developing  and  the  eggs  hatching  outside 
the  body  of  the  parent.  Very  rarely  there  appears  an  object  that  looks 
very  much  like  an  egg.  There  are  no  free  appendages  or  other  char- 
acters common  to  the  young  insect.  But  if  this  is  placed  under  a 
microscope  or  examined  closely  with  a  lens  it  will  be  seen  that  there  is 
a  perfectly  developed  young  insect  within  which  is  surrounded  by  an 
enveloping  membrane — the  amnion.  This  encloses  the  developing  larva, 
and  ordinarily  is  cast  off  within  the  oviduct,  but  occasionally,  as  inti- 
mated, this  is  not  cast  off  until  it  is  outside  the  oviduct.  The  larva 
emerging  from  beneath  the  parent  scale,  where  it  may  have  remained  for 
a  day  or  two  after  birth,  crawls  about  for  a  day  or  two  longer  before 
settling  and  becoming  fixed.  It  is  most  usual  to  find  them  settling  on  the 
following  day,  but  if,  in  the  mean  time,  a  suitable  place  for  becoming 
stationary  and  obtaining  food  is  not  found,  they  may  remain  active  for  a 
day  or  two  longer.  They  do  not  as  a  rule  migrate  very  far  from  their 
parent  scale.  Several  oranges,  badly  infested  with  red  scale  which  were 
producing  young,  were  each  placed  in  a  young  orange  tree  that  was 
entirely  free  from  scale.  Two  or  three  weeks  later  those  trees  were 
examined  to  determine  if  any  had  settled  on  the  tree.  Hundreds  of 
young  scales  with  their  white  circular  covering  were  found,  and  imme- 


110 


UNIVERSITY  OF   CALIFORNIA EXPERIMENT   STATION. 


diately  about  the  fruit  for  a  few  inches  the  branches  and  leaves  were 
simply  peppered  with  young  scales.  As  the  distance  from  the  point  of 
liberation  increased  the  number  of  scales  decreased,  and  the  maximum 
distance  they  were  found  to  travel  and  become  fixed  was  19  inches  above 
on  one  tree  and  21  inches  below  on  another.  The  tree  was  succulent  and 
thrifty  and  offered  suitable  ground  for  settling  without  much  crawling 
about.  In  other  cases  they  are,  of  course,  likely  to  go  farther,  and,  in 
addition  to  their  own  powers  of  traveling,  they  may  be  distributed  about 
by  other  insects.  A  fuller  discussion  of  the  subject  of  locomotion  is  given 
under  the  head  of  "Locomotion  and  Spread." 


Temperature  and  humidity  records  covering  period  when  most  of  the  life  history  data 
on  Chrysomphalus  aurantii  were  secured. 


1909— February 
March    ___ 

April    

May 

June   

July    

August  _. 
September 
October  _ 
November 
December 


Humidity  (means). 

Temper 

i 
Mean 

7  A.  M. 

12  M. 

5  P.  M. 

minimum. 

91 

65 

80 

44 

84.4 

62 

74.9 

45.6 

83.4 

56 

69 

50.7 

83 

57.7 

66.5 

53 

83.5 

63.4 

65.9 

57.1 

85.4 

59.9 

68 

59 

82.6 

50.1 

59.1 

57.2 

85.4 

56.1 

72.5 

58.9 

83.1 

55.2 

75.5 

52.8 

83.1 

58 

78 

45.9    i 

81.6 

74.9 

80.6 

44        | 

Mean 
maximum. 


73.2 
76 

80.1 

81.3 

84.2 

87.1 

93.1 

90.8 

84 

75.8 

73 


SETTLING  OF  THE  LARV2E. 

A  few  larvae  will  settle  down  on  the  same  day  of  emergence,  but  the 
great  majority  will  be  found  to  settle  on  the  following  day.  Daily  records 
of  emergence  were  made  on  about  1000  scales,  and  out  of  this  number 
they  would  be  occasionally  found  to  settle  before  examination  on  the 
following  day.  Records  kept  on  884  young  larvae  liberated  in  leaf  cages 
showed  that  about  95  per  cent  settled  within  one  day.  But  here  the 
larvae  were  picked  from  infested  fruit  as  they  were  actively  crawling 
about,  so  that  some  may  have  been  emerged  for  some  time. 

The  proportion  settling  and  becoming  established  in  our  cages  was 
41  per  cent.  These  were  liberated  on  leaves  and  had  practically  normal 
conditions.  The  fact  that  they  were  enclosed  in  cages  and  thus  protected 
from  enemies  or  becoming  dislodged  and  falling  to  the  ground,  was 
really  in  favor  of  a  greater  number  becoming  fixed  than  would  be  the 
case  were  they  out  in  the  open.  The  insects  were  transferred  by  a  small 
camel 's  hair  brush  or  a  needle.  Possibly  some  may  have  been  injured  in 
the  transfer,  but  care  was  taken  in  this  regard,  and  usually  the  count  of 
the  number  liberated  was  made  of  those  actually  crawling  about  and 
unharmed  in  the  cages. 


Bulletin  222] 


THE   RED   OR   ORANGE   SCALE. 


Ill 


The  following  table  shows  the  number  that  settle,  and,  since  these 
experiments  were  extended  over  several  months  of  the  year,  there 
appears  to  be  little  effect  due  to  season: 


5-'  3 


1908— September  21 
September  23 
September  23 

September   23 
November  24 
1909— January   30    . 

June   19   

June   19    

July    2    

July    2    

July    2    

July    3    

July    21    

July    24    

August  12  ___ 

August  13  

August  18  

August  ]8  ___. 

August  IS  

August  21  ___. 
September  2  . 
September  2  . 
September  3  . 
September  3  . 
September  4  . 
September  4  . 
September  7  . 
September  7  . 
September 
September  22 
September 
September 
September 


1909— September  22 
September  22 
September  30 
October  1   ___ 

October  1   

October  4   ___ 

October  5  

October  11  __. 
October  11  __. 
October  11  „ 
October  13  __. 
October  14  __ 
October  20  __. 
October  20  __. 
October  21  __. 
November  26  . 

1910— May  31  

May  31  

May  31  

June  3   

June  6   

June  6   

June  17   

June   17   

June   20    

June   20   

June  20   

June  20    

June  20   


Total   

Per  cent  settled,   41.06. 


884 


They  may  settle  either  on  the  leaves,  branches  or  fruit.  It  seems  to 
make  no  very  great  difference  where  they  settle  so  long  as  it  is  con- 
venient. But  the  part  of  the  tree  that  is  more  likely  to  be  severely 
infested  first  is  the  branches,  later  the  leaves,  and  finally  the  fruit. 
They  will  be  found  on  both  sides  of  the  leaves,  but  the  upper  side, 
usually,  has  the  greater  numbers.  In  the  case  of  the  yellow  it  is  more 
often  the  under  side.  The  red  will  not  settle  readily  on  the  older  and 
larger  corky  branches,  but  prefer  the  younger  succulent  branches  where 
not  so  much  of  the  corky  material  has  been  deposited. 


FORMATION  OF  THE  SCALE  COVERING. 

When  the  active  larva  first  settles  the  legs  and  antennae  are  withdrawn 
beneath  the  body  and  in  an  hour  or  two  a  cottony  secretion  appears 
from  numerous  pores  over  the  body.  In  another  hour  a  light  flimsy 
covering  of  cottony  threads  envelops  the  entire  scale  and  extends  down 
over  the  sides  of  the  insect  to  the  surface  on  which  it  is  resting.  The 
2— bul.  222 


112 


UNIVERSITY   OF   CALIFORNIA EXPERIMENT   STATION. 


Fig.  10. — 1  Different  stages  in  formation  of  scale  covering.  2  The 
ventral  scale  formed  beneath  the  insect.  3  Old  and  young  red 
scales  on  orange.  4  Larva  of  parasite,  Aphelinus  diaspidis,  feed- 
ing on  Red  Scale ;  the  scale  shriveled  from  absorption  of  body 
contents.  5  Yellow  scale  containing  pupa  of  parasite  Aspid- 
iotiphagus  citrinus.  ' 


Bulletin  222]  THE  RED  0R  0RANGE  SCALE.  113 

covering  is  still  transparent  enough  to  see  plainly  the  insect  beneath. 
By  this  time  the  insect  itself  has  shortened  in  length,  while  its  width  is 
increased,  and  it  thus  becomes  almost  circular.  While  this  covering  is 
being  secreted  the  insect  beneath  revolves  about  for  the  purpose  of 
molding  the  covering  in  the  proper  form. 

It  is  generally  assumed  that  the  insertion  of  the  beak  into  the  plant 
tissue  is  a  necessary  preliminary  operation  to  the  secretion  of  the  cover- 
ing. On  this  point  our  observations,  in  general,  seem  to  agree,  but  the 
actual  operation  of  inserting  the  beak  can  not  be  seen  readily.  They 
have  been  seen  to  settle  with  the  beak  inserted  and  then  withdrawn 
again  before  any  covering  is  started.  The  withdrawal  of  the  beak  has 
been  noted  in  a  few  instances,  and  the  process  is  characterized  by  more 
distinct  indications  than  is  the  case  with  the  insertion.  A  considerable 
movement  of  the  body  occurs  by  turning  partly  around,  and  also  a  rapid 
movement  of  the  legs  and  antennae.  Certain  cases  have  been  observed 
where  the  young  scales  settled  on  top  of  an  old  one  and  secreted  the 
preliminary  covering,  yet  the  depth  of  the  old  scale  was  too  great  to 
allow  the  young  one  above  to  reach  the  plant  tissues.  In  such  cases  the 
covering  is  commenced  before  the  beak  is  inserted  or  at  least  before  any 
food  is  taken.  It  often  happens,  of  course,  that  young  settle  on  the 
outer  margins  of  the  old  scales,  but  here  there  is  no  difficulty  in  reach- 
ing through  to  the  plant  substance  beneath. 

The  same  insect  may  secrete  a  new  covering  for  a  few  times  if  the 
old  one  is  removed.  A  scale  covering,  one  or  two  days  old,  was  lifted 
from  the  insect  and  again  replaced.  It  accepted  the  new  covering,  and 
four  days  later  it  was  again  lifted,  and  again  replaced.  This  time  the 
covering  was  not  accepted,  but  a  new  covering  was  secreted.  In  the  case 
of  other  insects  the  covering  was  permanently  removed,  and  the  maxi- 
mum number  of  new  coverings  formed  was  four.  When  the  covering 
was  removed  three  or  four  times  or  more  the  insect  died. 

A  couple  of  days  after  settling  the  covering  is  more  compacted, 
especially  on  the  sides  near  the  surface  upon  which  the  insect  is  resting. 
The  dorsal  surface  is  still  light  and  fluffy,  but  thick  enough  to  entirely 
conceal  the  insect  beneath.  The  form  at  this  time  is  that  of  a  cap  with 
a  flat  dorsal  surface  and  straight  vertical  sides.  After  a  few  days  this 
sinks  down  immediately  around  the  center  leaving  a  small  prominence 
forming  the  so-called  nipple.  As  the  scale  covering  increases  in  size,  it 
spreads  out  with  a  thin  edge  forming  the  margin  instead  of  the  vertical 
wall  as  was  the  case  earlier.  In  a  week  or  two  all  the  cottony  effect  is 
Jost,  and  the  covering  becomes  a  very  compacted  film.  In  eighteen  to 
twenty  days  the  cast  skin  of  the  insect  may  be  seen  incorporated  into 
and  forming  the  greater  part  of  the  covering.  With  the  increased  size 
of  the  insect  after  the  molt  it  becomes  necessary  to  enlarge  the  covering, 


114 


UNIVERSITY   OF   CALIFORNIA EXPERIMENT   STATION. 


and  this  is  extended  beyond  the  cast  skin,  which  soon  comes  to  form  but 
the  center  of  the  scale  covering.  A  similar  cast  skin  is  incorporated 
into  the  covering  after  the  second  molt  which  is  about  twice  the  size  of 
the  first.  Thus  the  two  cast  skins  may  be  seen  forming  two  nearly 
concentric  circles.  The  covering  is  again  extended,  being  secreted  and 
added  to  the  outer  margin  until  the  total  width  may  be  twice  that  of 
the  second  cast  skin.  During  this  formation  of  the  scale  the  lobes  and 
p]ates  of  the  pygidium  play  an  important  part  in  molding  it  into  the 
proper  form.  The  insect  during  the  process,  must  revolve  around  to 
reach  the  margin  with  the  posterior  tip  of  the  body  which  is  capable  of 
being  greatly  extended  or  contracted  as  required. 


Fig.  11. — 1  Scale  of  male.     2  Scale  of  female,  same  magnification, 
male  scale,  showing  winged  insect  beneath. 


3  Inverted 


The  above  account  has  reference  to  the  female  scale  only.  The  scale 
of  the  male  is  exactly  the  same  until  after  the  first  molt,  but  from  that 
stage  on  it  takes  on  a  very  different  form  from  that  of  the  female.  The 
male  insect  itself  during  the  second  stage  becomes  much  more  elongate 
and  so  the  scale  covering  assumes  a  corresponding  shape.  After  the  first 
molt  the  male  scale  covering  widens  but  little,  but  increases  consider- 
ably in  length,  so  that  the  mature  scale  is  about  twice  as  long  as  broad. 
But  its  extreme  length  is  not  as  great  as  the  diameter  of  the  mature 
female  scale.  The  average  size  of  the  mature  female  scale  is  about 
1.5  mm.  in  diameter,  while  the  mature  male  scale  is  about  1  mm.  in 
length. 

THE  FIXED   YOUNG. 

Molting.  After  the  insect  has  settled  and  the  covering  secreted  it 
undergoes  no  change,  except  to  increase  in  size,  until  after  the  first  molt. 
This  molt  occurs  in  from  fourteen  to  twenty  days  after  settling.  Prelim- 
inary to  molting,  the  insect,  which,  up  to  this  period  is  readily  separated 
from  the  scale  now  becomes  firmly  attached  to  it.  Previous  to  this  time 
the  bodv  of  the  insect  has  a  flexible,  and  somewhat  tough  covering,  and  is 


Bulletin  222 J 


THE  RED  OR  ORANGE   SCALE. 


115 


not  much  distended  by  the  contents.  But  during  the  molting  period, 
which  lasts  from  three  to  five  days,  the  body  wall  is  hard  and  brittle 
and  well  distended.  The  body  contents  seem  to  be  much  more  fluid  and 
watery  during  this  period.  This  change  in  the  body  wall  and  its  con- 
tents is  shown  during 
the  handling  of  the 
insect  with  a  needle. 
Between  the  molts 
punctures  are  less 
likely  to  occur  for  the 
reason  of  the  flexibility 
of  the  skin,  while  it  is 
very  readily  punctured 
through  the  firm  dis- 
tended skin  during  the 
molts. 

The  skin  is  split 
around  the  lateral  mar- 
gin, not  only  around 
the  general  body  mar- 
gin, but  often  the  mar- 
gin of  the  lobes  and 
plates  also.  If  the  cast 
dorsal  s'kin  be  treated 
in  potash  the  lobes, 
plates  and  spines  show 
nearly  as  clearly  as  in 
the  insect  itself  in 
some  of  the  specimens. 
If  the  very  frail  and 
almost  invisible  cast  ventral  skin  be  examined  most  of  the  pygidial 
characters  will  also  be  seen  in  some  of  the  specimens.  Some  times 
greater  detail  of  the  pygidial  structures  is  shown  in  the  ventral  and 
some  times  in  the  dorsal  cast  skin.  The  figures  Nos.  12  and  13  indicate 
this.  In  the  first  ventral  skin  the  legs,  antenme  and  mouth  parts  are 
of  course  present. 

The  molting  of  the  male  differs  very  strikingly  from  that  of  the 
female  excepting  the  first  molt  which  is  the  same  in  both  cases.  Instead 
of  the  skin  splitting  around  the  lateral  margin  as  is  the  case  with  the 
female,  the  rent  occurs  near  the  anterior  end,  and  the  old  skin  is  pushed 
backward  and  from  under  the  scale.  These  cast  skins  may  often  be  seen 
still  attached  to  the  posterior  tip  of  the  scale. 


Fig.   12. — a  Dorsal  view  of  pygidium  of  Red  Scale, 

x200. 
b  Ventral  cast  skin  of  Red  Scale.     Prom  same  in- 
sect as  Fig.  13,  3,  which  is  the  dorsal  cast  skin. 


116 


UNIVERSITY  OP   CALIFORNIA — EXPERIMENT   STATION. 


Fig.  13. — 1  A  cast  skin  after  first  molt.  2  A  ventral  cast  skin,  second  molt. 
3  Dorsal  cast  skin,  second  molt,  same  insect  as  Fig.  12,  b,  which  shows 
the  ventral  cast  skin.     4  Characters  of  complete  insect.     x350. 

The  second  molt  of 
the  male  insect  occurs 
in  about  thirty  days 
from  birth  which 
brings  it  to  the  pro- 
pupal  stage.  It  re- 
mains in  this  stage 
about  ten  days  when 
the  third  molt  occurs 
after  which  it  is  in 
the  true  pupal  stage. 
Ten  or  twelve  days 
are  spent  as  a  true 
pupa  when  it  trans- 
forms to  the  adult. 
The  adult  remains 
beneath  the  scale  from 
three  to  five  days  be- 

Fig.  14.— Showing  the  mature  Red  Scale  with  its  cast  skins    ^ore    emerging.       The 
and  the  scale  covering.       1  First  cast  skin.       2  Second  cast    QVinrfpct       r>PT»inrl       rp 
skin.      3   The  insect  itself.      4   The   scale  covering.     x60.    ouw-^&u       penuu.       ic- 


Bulletin  222] 


THE   RED   OR   ORANGE   SCALE. 


117 


quired  for  the  development  of  the  male  was  found  to  be  55  days.  This 
was  from  June  20th  to  August  14th,  which  included  the  hottest  weather 
of  the  season  of  1910.  The  longest  period  determined  for  the  develop- 
ment of  the  male  was  112  days.  This  was  from  January  2  to  May  1, 
1909,  which  included  the  coldest  weather  of  the  season. 


THE  ADULT  MALE. 

The  male  pushes  its  way  backward  from  beneath  the  scale  and  actively 
walks  about  immediately  after  emerging.  Upon  transforming  to  the 
adult  it  remains  beneath  the  scale  for  a  few  days,  so  that  the  wings  are 
thoroughly  dried  and  expanded,  and  is  at  once  strong  enough  to  begin 
its  short  period  of  active  life.  It  usually  walks  about  on  the  leaf  or 
fruit  for  a  short  time,  and  then  flies  away.  This  appears  to  be  a  provi- 
sion to  insure  the  fertilization  of  females  some  little  distance  away,  and 
thus  prevent  possible  degeneration  through  in-breeding  with  the  females 
of  the  same  parent  which  usually  settle  down  in  the  immediate  vicinity. 
Copulation  may  occur  within  a  half  hour  or  hour  after  emergence.  The 
adult  life  varies  from  one  to  five  days.  The  male  of  this,  like  most 
other  scale  insects,  is  not  a  strong  flier,  but  may  be  greatly  aided  in 
prolonged  flights  by  the  wind.  They  appear  to  be  more  abundant  at 
certain  seasons,  and  this  is  particularly  true  of  the  early  spring.  The 
following  table  gives  the  proportion  of  the  sexes  according  to  the  time 
liberated  which  includes  most  of  the  months  of  the  year.  It  will  be 
seen  from  this  that  during  the  first  half  of  the  year  the  number  of 
males  was  74  while  the  number  of  females  was  42.  During  the  second 
half  of  the  year  the  sexes  were  approximately  equal,  the  table  giving  34 
for  the  males  and  35  for  the  females : 


FIRST     HALF-TEAR. 

SECOND     HALF-YEAR. 

Young  liberated. 

Number 
males. 

Number 
females. 

Young  liberated. 

Number 
males. 

Number 
females. 

7 
6 
7 
22 
5 
3 
7 

5 
2 
2 
2 
2 
0 
2 
4 

3 

1 
4 
8 
3 
3 
4 
3 
1 
3 
4 
1 
3 
0 
1 

2                   2 

February  24__      

2                   1 

May           12 

September    3  _    __    __    

2                   1 

May           13__    _ 

September    7 

1                   1 

June             3__    _ 

September  22  . 

7                   2 

1        ,          1 

June            7 

5                  5 

June           17 

October       11 

4                   2 

June           17  _    __ 

1    October       13_. 

0                   3 

June           17 _. 

October      14 

2                   1 

June           18  _._ 

October       20__    _  _ 

1                   2 

June           18_    

November  10__ 

2                   4 

June          19_ 

November  29 -        -    

0                  3 

June           19 

Total   __    __ _ 

July           24 

Total   

74 

42 

34 

35 

118 


UNIVERSITY   OP   CALIFORNIA EXPERIMENT   STATION. 


THE  ADULT  FEMALE. 

The  second  molt  of  the  female  occurs  from  40  to  50  days  after  birth, 
which  brings  it  to  the  adult.  It  continues  to  secrete  the  scale  covering 
after  this  molt  to  allow  for  its  increased  growth.  From  10  to  20  days 
after  the  second  molt  it  is  fertilized  by  the  male.  This  is  on  an  average 
about  60  days  from  birth.  The  formation  of  the  scale  is  entirely  com- 
pleted before  the  production  of  young  is  commenced.  During  the 
period  the  insect  is  producing  young  it  is  similar  to  that  of  the  molting 
periods.  That  is,  the  insect  itself  is  inseparable  from  the  scale,  and  the 
body  is  rigid  and  distended. 


LENGTH  OF   ADULT  LIFE. 

The  female  scales  begin  to  produce  young  in  about  ninety  days,  and 
this  is  continued  from  one  to  two  months  longer,  making  the  total  life 
of  the  adult  from  four  to  five  months.  In  case  the  female  is  not 
fertilized  the  adult  life  may  be  extended  much  longer.     Five  females 


;''"l«.irii  L  ii(*-^^WPH 

/:■-  :;;:^p;' 

BP  i  l^-^^mj 

™             ~4t 

HBj£U     '                  thgfljfi^. 

Gftri     w 

■**' 

^'**fE?:^~ +Jk 

Fig.  15. — Red  Scale,  mature  females  and  young. 

isolated  in  cages  were  perfectly  healthy  and  vigorous  and  not  yet  having 
produced  young  after  a  period  of  five  months  and  twenty-six  days. 
This  was  during  the  warmest  part  of  the  season,  from  May  31st  to 
November  25th,  when  cold  was  not  a  factor  in  retarding  development. 
This  fact  was  learned  in  connection  with  the  experiments  on  partheno- 
genesis. When  insects  liberated  at  the  same  time  were  fertilized  and 
had  completed  their  production  of  young  the  leaves  containing  the 
unfertilized  scales  were  unfortunately  removed  from  the  tree  for  exam- 
ination.    This  prevented  us  from  obtaining  the  maximum  life  of  the 


Bulletin  2221 


THE   RED  OR   ORANGE   SCALE. 


119 


unfertilized  female,  and  also  from  determining  if  they  could,  at  that 
late  date,  be  fertilized  and  still  produce  their  quota  of  young-.  This 
latter  fact  will  very  probably  be  true,  but  as  yet  the  evidence  of  actual 
trial  is  not  at  hand.  In  case  the  female  is  not  fertilized  it  thus  appears 
that  its  development  is  practically  at  a  standstill  for  at  least  three 
months,  or  it  wTill  live  for  at  least  three  months  after  reaching  maturity 
without  producing  young. 

AGE  AT  WHICH  YOUNG  IS  PRODUCED. 

The  minimum  period  from  birth  to  the  appearance  of  young  was 
found  to  be  73  days.  This  was  from  June  20th  to  September  1st,  which 
included  the  warmest  weather  for  the  season  of  1910.  This  was  at 
Riverside,  where  the  temperature  is  higher  than  that  of  Whittier,  where 
the  most  of  the  work  was  done.  Parallel  experiments  carried  on  during 
the  same  period  showed  the  minimum  period  from  birth  to  the  produc- 
tion of  young  as  81  days  at  Whittier. 

The  maximum  period  was  from  February  24th  to  June  30th,  or  four 


I                                                 •  '"V«~A»* lit   •  *      ''*  '    /'  *' 

I' 

VV7 

jr    A-         ri^   '"       fl 

Fig.   16. — Red  Scale   (Chrysomphalus  aurantii  Mask.)   on  grape  fruit. 

months  and  ten  days.  Young  born  on  January  2d  did  not  produce 
adult  males  until  May  1st.  Allowing  the  usual  thirty  days  from  fertil- 
ization to  the  appearance  of  young  would  make  a  period  of  five  months. 


120 


UNIVERSITY  OF   CALIFORNIA EXPERIMENT   STATION. 


This  represents  the  maximum  for  the  coldest  weather  of  the  season. 
The  age  at  which  young  is  produced  is  also  dependent  upon  the  time  of 
fertilization.  Scales  may  live  for  four  or  five  months  during  the 
warmest  part  of  the  year,  and  then  after  fertilization  very  probably 
produce  young. 


ASPIDIOTUS    AURANTII  — DEVELOPMENT. 


Experi- 
ment 
number 

Date 

Settled. 

First 
molt. 

Second 
molt  2 

Second 
molt  o 

d  Propupa 

$  Pupa. 

6  Emerged 

O    Dead. 

Young 
appeared. 

14___ 

9-23-08 

9-24 



11-25 

12-  1 

1-  2-09 

33— 

1-  2-09 

1-  3 

4-16 

5-  1 

5-  5 

104... 

2-24 

2-25 

3-16 

4-20 

3-30 

4-16 

5-11 

5-15 

6-30 

102... 

2-20       *         2-21 

3-16 

4-20 

3-30 

4-  8 

1(XL__ 

2-24 

6-26 

139... 

5-  4 

5-  6 



6-28 

8-  6 

146— 

5-12 

5-13 



7-14 

149... 

5-  9 

5-10 



7-3 

7-18 

7-22 

8-10 

150 

5-19 

5-21 

6-  4 

6-15 

6-30 

7-21 

8-18 

151... 

5-19 

5-20 

6-  6 

7-10 

7-  2 

7-21 

161— 

5-21 

5-23 



7-14 

7-21 

7-26 

8-  7 

148— 

5-13 

5-14 

6-1 

6-30 

6-22 



7-12 

7-16 

173— 

6-  4 

6-  5 







9-  8 

182— 

6-17 

7-12 

7-21 



183— 

6-17 



7-27 

7-21 

8-11 

184___ 

6-17 

6-18 

7-1 





7-21 

8-11 

8-16 



187— 

6-18 

7-  3 

8-11 





189— 

6-18 

7-28 

7-21 

8-11 

8-15 

190— 

6-19 

7-  3 

9-10 

191— 

6-19 

8-  1 

7-14 



8-14 

192_._ 

6-19 

7-  5 

7-17 



9-10 

193— 

6-19 

7-17 



215___ 

7-  2 

7-  4 

8-11 

8-24 

214... 

7-2 

7-17 

7-28 

8-11 

217— 

7-  3 



8-11 

8-24 

9-10 

9-14 

256___ 

7-21 

7-23 

8-5 

8-16 

260 

7-24 

9-  9 

10-  6 

279— 

8-12 



9-20 

10-10 

10-14 

11-24 

285__. 

8-12 

8-13 

10-12 



11-27 

311_-_ 

9-  2 

9-18 

10-15 

10-20 

10-29 

11-  2 

1-18-10 

312_._ 

9-  3 

9-20 

10-29 



322... 

9-22 

12-  2 

323— 

9-22 

10-  5 

10-18 

10-29 

12-  2 

12-  6 

325... 

9-22 

9-23 

10-29 

11-30 





326... 

9-22 

10-12 

11-  6 



12-  5 

12-  8 

327— 

9-22 

9-24 

10-14 

10-29 



1-  2-10 

335 

10-  5 

10-25 



1-2 



341— 

10-11 



1-11 



342. __ 

10-11 

10-30 

1-15 

1-20 



347... 

10-14 



1-27 

3-25 

559... 

6-17-10 



7-20 

7-16 

7-28 



8-4 





561... 

6-17 



7-3 

7-21 



563... 

5-31 

7-28 

564... 

5-31 

6-1 

8-  1 





568. __ 

6-  6 



7-27 

8-  4 





569... 

6-6 

7-12 

*570... 

6-20 

7-  4 

8-14 

9-  1 

*571.._ 

6-20 

*572 

6-20 



7-  4 

9-  2 

*573— 

6-20 



8-14 



9-  1 

Summa 

ry  av  ... 

24hrs. 

16  days 

46  days 

30  days 

38  days 

48  days 

60  days 

65  days 

90  days 

cAt  Riverside. 


Bulletin  222] 


THE  RED   OR   ORANGE   SCALE. 


121 


EMBRYONIC  DEVELOPMENT. 

Since  the  female  comes  to  maturity  and  is  fertilized  by  the  male  about 
sixty  days  from  birth,  and  the  production  of  young  begins  on  an  average 
of  ninety  days,  the  time  required  for  the  development  of  the  egg  and 
the  hatching  of  the  larva  therefrom  within  the  body  of  the  female,  is 
about  thirty  days. 


Fig.   17. — Greedy  Scale    (Aspidiotus  rapax  Comst. ). 
mistaken  for  Red  Scale. 


Sometimes 


PARTHENOGENESIS. 

Several  individual  female  red  scales  were  isolated  as  they  approached 
maturity,  and  no  males  allowed  to  reach  them.  In  every  case  no  young 
appeared  under  such  conditions.  These  lived  for  a  period  of  more  than 
six  months,  with  no  indication  of  young  appearing.  The  insect  remained 
in  the  condition  it  was  after  the  second  molt,  that  is,  it  was  free  from 
the  scale  covering  and  with  a  pliable  body,  as  opposed  to  the  gravid 
condition  or  molting  periods,  or  young-producing  periods,  'as  already 
explained. 

EMERGENCE  OF  YOUNG. 

The  emergence  of  young  means  practically  the  same  as  the  birth  of 
young,  but  since  the  actual  birth  records  can  not  be  obtained  without 
destroying  the  parent,  emergence  is  used  in  this  discussion  rather  than 
birth.    This  makes  no  difference  in  the  total  number,  or  the  length  of  the 


122  UNIVERSITY  OF   CALIFORNIA — EXPERIMENT   STATION. 

producing  period,  though  it  may  make  some  difference  in  the  rate  from 
day  to  day.  That  is,  when  a  sudden  drop  in  the  temperature  occurs, 
for  instance,  the  young  already  born  may  linger  under  the  scale  for  a 
longer  period  than  would  otherwise  be  the  case.  But  the  records  given 
show  that  there  is  little  variation  on  this  point.  The  maximum  number 
emerged  in  a  single  day  was  found  to  be  eight.  But  five  or  six  may 
appear  for  three  or  four  days  in  succession,  showing  that  this  number 
must  actually  be  produced  on  those  days. 

The  records  given  in  the  table  are  for  fourteen  females,  of  which  daily 
examination  was  made  throughout  the  producing  period.     Many  other 


» « v             # 

-  d  .  .    £'t 

*    •  .- 

•■-•'.         f 

;-:;■■  v  J 

UlKti^mmm 

ummmmg^A 

Fig.  18. — Red  Scale  on  orange  leaf. 

records  were  less  accurately  made.  The  period  during  which  young 
were  produced  varied  from  16  to  63  days,  with  an  average  of  about  23. 
The  number  of  young  per  insect  varied  from  34  to  143,  with  an  average 
of  55.  The  number  of  young  appearing  in  a  day  was  from  0  to  8.  The 
average  number  of  young  per  day  for  the  different  scales  ran  from  1.65 
to  3.07,  with  an  average  for  the  total  number  of  scales  of  2.33.  These 
records  on  the  production  of  young  were  made  during  the  months  of 
September  and  October  mostly.  September  in  southern  California  is  a 
fairly  warm  month,  and  during  October  it  seldom  gets  cool  enough  to 
have  any  marked  effect  on  the  activity  of  the  scale.  Records  on  the 
emergence'  of  young  during  June  and  July  showed  that  it  was  prac- 
tically the  same  as  that  of  September  and  October.  Those  given,  there- 
fore, may  be  considered  as  a  fair  average  for  the  active  season  from 
April  to  November. 


Bulletin  222] 


THE   RED  OR   ORANGE   SCALE. 
EMERGENCE   OF   YOUNG. 


123 


Date,  11)10. 


Date,  1910. 


Sept . 

Sept. 

Sept. 

Sept. 

Sept. 

Sept . 

Sept. 

Sept. 

Sept. 

Sept. 

Sept. 

Oct. 

Oct . 

Oct. 

Oct. 

Oct. 

Oct . 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Nov. 

Nov. 

Nov. 

Nov. 

Nov. 

Nov. 

Nov. 

Nov . 

Nov. 

Nov. 

Nov. 

Nov . 

Nov. 

Nov . 

Nov. 

Nov. 

Nov. 

Nov. 

Nov. 

Nov. 

Nov. 


28. 


Total  

Day-  

Av.  per  day. 


Sept. 

Sept. 

Sept. 

Sept. 

Sept. 

Sept. 

Sept. 

Sept. 

Sept. 

Sept. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 


22 
23 

24 
25 
26. 
27. 
28. 
29. 
30. 

1. 

2 

3. 

4. 

5. 

6. 

8. 

lo. 


Total  

Days  

Av.  per  day. 


Sept.  24 

Sept.  25 

Sept.  20 

Sept.  27 

Sept.  28 

Sept.  29 

Sept.  30 

Oct.   1 

Oct.   2 

Oct.   3 

Oct.   4 

Oct.   5 


0  !Oct. 


Oct. 
Oct. 
Oct. 
Oct. 
Oct. 
Oct. 
Oct. 
Oct. 
Oct. 
Oct. 
Oct. 
Oct. 
Oct. 


20 


Total 
Days  __. 


1.65  J  Av.  per  day. 


Sept. 

Sept. 

Sept. 

Sept. 

Sept. 

Sept. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct . 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 


Total 

Days 

Av.  per  day. 


25 

3.56 


Sept.  28 

Sept.  29. 

Sept.  30. 

Oct.  1. 

Oct.  2 

Oct.  3. 

Oct.  4. 

Oct.  5. 

Oct.  6. 

Oct.  7. 

Oct.  8. 

Oct.  9. 

Oct.  10. 

Oct.  11. 


Total 

Days  

Av.  per  day. 


124 


UNIVERSITY  OF   CALIFORNIA EXPERIMENT   STATION. 


EMERGENCE    OF    YOUNG— Continued. 


Date,  1910. 


Sept.  28 

Sept.  29 

Sept.  30 

Oct.  1 

Oct.  2 

Oct.  3 

Oct.  4 

Oct.  5 

Oct.  6 

Oct.  7 

Oct.  8 

Oct.  9 

Oct.  10 

Oct.  11 

Oct.  12 

Oct.  13 

Oct.  14 


Total  

Days  

Av.  per  day. 


Is 


Date,  1910. 


8    Sept.  29. 

3  Sept.  30. 

1  Oct.  1. 

4  Oct.  2. 

2  Oct.  3. 

3  Oct.  4. 

5  Oct.  5. 

6  Oct.  0. 
6  Oct.  7. 
8    Oct.  8. 

4  Oct.  9. 
3  Oct.  10. 
0  Oct.  11. 
O.Oct.  12. 

0  Oct.  13 
3    Oct.  14 

1  Oct.  15. 
Oct.  16 
Oct.  17 
Oct.  18 
Oct .  19. 


Date,  1910. 


Sept. 

Sept. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

0  Oct. 

2  !  Oct. 

3  |  Oct. 
2  (Oct. 

1  |  Oct. 
0|Oct. 

11  j  Oct. 
] 


57 

Total 

42 

17 

Days  

21 

35 

Av.  per  day__ 

2 

Total 


Days 


Sept. 
Sept. 
Sept. 
Sept. 
Sept. 
Sept. 
Sept. 
Sept. 
Sept. 
Sept. 
Sept. 
Sept. 


Sept. 
!  Sept. 

Oct. 
S  Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 

Oct. 


20 


Av.  per  day__  3.05 


Sept.    19_ 


4 
4 

4 
4 
4 
5 
6 
3 

0  |  Sept.    20 

1  Sept.    21 

0  Sept.    22 

1  j  Sept.  23 
0  j  Sept.  24 
0  ;  Sept.    25 

2  |  Sept.    26 

Sept.    27 
Sept.    28 


2 

SI 


Total  

Days    

Av.  per  day. 


42 


Date,  1910. 


Total 
Days    „ 


Oct.  1. 

Oct.  2. 

Oct.  3. 

Oct.  4. 

Oct.  5. 

Oct.  6. 

Oct.  7. 

Oct.  8 

Oct.  9. 

Oct.  10 

Oct.  11. 

Oct.  12 

Oct.  13 


2 

o  5 

II 


Av.   per  day.  2.30 


Bulletin  222] 


THE  RED  OR   ORANGE   SCALE. 


125 


EMERGENCE    OF    YOUNG— Continued. 


g 

M  2 

2 

V. 

«<!   S= 

^  s 

■<  % 

Pate,  1910. 

*B 

Date,  1010. 

*S 

Date,  1910. 

yy 

Date,  1919. 

*B 

8  s 

w  J? 

k° 

October  1 
October  2 
October  3 
October  4 
October  5 
October  6 
October  7 
October  8 
October  9 
October  10 
October  11 
October  12 
October  13 
October  14 
October  15 
October  16 
October  17 
October  18 
October  19 


Total  

Days  

Av.    per   day. 


October 
October 
October 


34 

19 

1.79 


October    4  

0 

October    5 

1 

October    6 

2 

October    7 

1 

October    8 

0 

October    9 

0 

October  10 

0 

October  11 

5 

October  12 

7 

October  13 

5 

October  14  

6 

October  15 

2 

October  16 

2 

October  17 

2 

October  18 

3 

Total  

37 

Days  

18 

Av.    per   day 

2.05 

October  4 
October  5 
October  6 
October  7 
October  8 
October  9 
October  10 
October  11 
October  12 
October  13 
October  14 
October  15 
October  16 
October  17 
October  18 
October  19 


Total 
Days  _. 


50 


October  5 
October  6 
October  7 
October  8 
October  9 
October  10 
October  11 
October  12 
October  13 
October  14 
October  15 
October  16 
October  17 
October  18 
October  19 
October  20 


Total 


16  J  Days 


Av.    per   day <  3.12      Av.    per   day. 


50 

16 

3.12 


Grand  total  number  of  young 

Number  of   days   producing 

Average  number  per  day 

Number  of  insects 

Average  number  young  per  insect- 
Average  producing  period,  days... 


771 
330 
2.33 

14 

55 

23.57 


DO  THE  INSECTS  MOVE  AFTER  BECOMING  FIXED  ? 

The  statement  has  appeared  that  the  red  and  yellow  scales,  particu- 
larly the  yellow,  may  move  after  becoming  fixed.  This  statement  is 
based  upon  no  evidence,  but  upon  the  fact  that  there  appears  a  distinct 
streak  of  yellow  tissue  showing  where  the  beak  has  been  inserted,  and 
this  being  too  long  to  be  produced  without  some  movement  of  the  scale. 
Several  dozen  scales,  both  red  and  yellow,  were  surrounded  by  India  ink 
to  determine  this  point,  but  none  were  found  to  move  in  the  slightest 
degree.  It  was  observed  that  in  the  formation  of  the  scale  it  was 
extended  under  the  film  of  ink.  The  circle  of  ink  on  the  leaf,  which 
just  surrounded  the  young  scale  was  later  resting  on  the  scale  itself, 
which  had  extended  under  and  beyond  the  ink  film. 

Both  the  red  and  yellow  scales,  but  especially  the  yellow,  often  pro- 
duce a  yellowish  spot  about  the  point  of  puncture.  This  often  shows 
through  on  the  opposite  side  of  the  leaf.  Sometimes  this  spot  is  much 
larger  than  the  scale  itself.  It  may  appear  in  a  uniform  circle  with  the 
scale  as  a  center,  and  again,  the  discoloration  may  be  all  on  one  side. 
The  size,  shape  and  position  of  the  spot  may  thus  vary  considerably. 
That  the  spot  is  due  to  the  extraction  of  the  chlorophyll  from  the  cells, 


326  UNIVERSITY   OF   CALIFORNIA — EXPERIMENT   STATION. 

or  from  the  toxic  effect  of  the  insertion  of  the  beak,  seems  well  estab- 
lished. It  is  most  usual  for  the  yellowing  to  appear  in  circular  spots, 
and  these  areas  may  be  much  larger  than  can  be  reached  by  the  beak. 
That  these  areas  should  sometimes  take  on  different  forms,  even  to  the 
extent  of  a  narrow  streak,  is  not  improbable,  and  it  is  hardly  necessary 
to  take  the  movement  of  the  scale  into  consideration  to  account  for  it. 
Another  point  against  any  movement  is  the  fact  that  the  flimsy  ventral 
cast  skins  are  always  found  directly  beneath  the  mature  insect.  It  is 
scarcely  possible  that  these  would  be  pulled  along  with  it. 


SEASONAL  HISTORY. 

The  average  length  of  the  life  cycle  from  the  active  young  to  the 
appearance  of  young  again  is  about  three  months.  During  the  warmer 
weather  it  will  run  slightly  under  this,  and  during  the  coldest  weather 
it  will  run  considerably  more,  the  extremes  being  from  72  days  to 
nearly  150  days.  Four  generations  a  year  will  be  the  largest  number  in 
a  season.  It  is  not  unlikely  that  this  number  occurs  in  the  warmer  sec- 
tions— as  Redlands  and  Riverside.  But  in  most  sections  three  genera- 
tions, with  a  partial  fourth,  will  represent  the  actual  conditions.  Start- 
ing with  April  1st,  the  beginning  of  the  next  generation  will  be  about 
July  1st.  Those  young  appearing  at  this  time  will  be  producing  young 
themselves  by  the  first  of  October.  This  will  make  two  generations 
during  the  months  of  greatest  activity.  Those  young  appearing  in 
October  may  not,  as  our  life  history  work  has  shown,  give  rise  to  young 
again  before  February  or  March.  This  makes  three  full  generations, 
with  a  partial  fourth,  for  conditions  as  they  obtain  at  Whittier. 

ANNUAL   PROGENY. 

It  is  a  well  known  fact  that  citrus  trees  may  become  very  severely 
infested  with  red  scale  in  a  single  year,  and  with  a  two  years'  infesta- 
tion a  large  portion  of  the  tree  may  be  killed.  This  often  happens  after 
the  grove  has  been  fumigated,  and  it  is  charged  that  the  fumigation  has 
not  been  effective.  This  may  or  may  not  be  the  case.  But  even  if  the 
fumigation  has  not  been  well  done,  if  the  scale  is  carried  in  from  a 
neighboring  grove,  the  trees  will  be  badly  infested  again  within  a  year ; 
this  is  accounted  for  through  the  rapid  multiplication  of  the  insect. 
While  the  number  of  young  from  a  single  individual  is  not  nearly  so 
large  as  that  of  the  black  scale — not  more  than  one  fortieth  as  large — the 
increased  number  of  generations  make  the  number  much  greater  at  the 
end  of  the  year.  Counting  the  average  number  of  young  produced  by 
a  single  red  scale  at  55,  and  allowing  one  half  of  this  number  for  males, 
the  number  at  the  end  of  the  third  generation  will  be  more  than  40,000, 
and  the  number  at  the  end  of  the  fourth  generation  will  be  more  than  a 


Bulletin  222]  THE  RED  0R  ORANGE  SCALE.  127 

million.  These  figures  include  the  males,  but  since  the  males  feed 
during  the  first  two  stages,  or  for  a  period  of  thirty  days,  they  must  be 
counted  as  injuring  the  plant,  but  of  course  not  to  such  an  extent  as 
the  females.  While,  therefore,  a  black  scale  may  produce  forty  times 
as  man}'  young  as  the  red,  the  progeny  from  a  single  red  scale  at  the 
end  of  a  year,  with  four  generations,  will  be  five  hundred  times  as  many 
as  the  progeny  of  the  black,  which  has  but  one  generation.  Only  a  small 
per  cent  of  these,  to  be  sure,  actually  comes  to  maturity,  but  it  is  an 
indication  of  what  might  be  approached  if  all  conditions  were  favorable. 

MORTALITY. 

One  of  the  most  critical  periods  in  the  life  of  the  red  scale  is  during  its 
active  larval  period.  Not  only  is  it  more  exposed  to  the  attack  of  enemies 
of  all  kinds,  but  its  own  failure  to  become  established  is  a  serious  check 
on  its  numbers.  The  actual  figures  given  earlier  in  this  account  show 
that,  under  the  favorable  conditions  of  being  protected  from  outside 
agencies,  the  number  settling  amounts  to  but  41  per  cent  of  those  that 
are  active.  More  than  one  half  is  thus  lost  before  they  have  scarcely 
started  on  their  life  cycle.  Many  of  those  that  do  settle  fail  for  one 
cause  or  another  to  reach  maturity.  The  molting  periods  are  other 
critical  stages,  and  many  fail  to  pass  successfully  through  these. 
Weather  conditions  may  also  be  factors  tending  to  decrease  their  num- 
bers, but  these  are  not  so  specifically  isolated  as  in  the  case  of  the 
influence  of  hot  weather  on  the  black  scale.  Parasites  and  predatory 
enemies  are  other  agencies  that  affect  the  number  of  the  red  scale  in  all 
stages,  but  these  will  be  discussed  later. 

LOCOMOTION  AND  SPREAD. 

The  red  scale,  like  most  other  scale  insects,  is  distributed  over  long 
distances  mainly  through  the  interchange  of  nursery  stock  or  the 
marketing  of  fruit.  This  scale  very  readily  attacks  the  fruit,  and  they 
may  live  on  this,  as  in  case  of  the  lemon,  for  many  months  after  being 
harvested.  Professor  Coit  of  this  station  wrapped  a  few  lemons  in 
ordinary  newspaper  and  stored  them  away  in  his  house  on  December  5, 
1909.  These  apparently  had  a  few  scattering  scales  which  were  not 
noticed  at  the  time  of  storing.  On  June  30,  1910,  or  nearly  seven 
months  later,  these  were  unwrapped,  and  upon  examination  were  found 
to  be  badly  infested  with  the  red  scale.  Altogether  there  were  35  adults, 
and  between  800  and  900  young,  all  alive.  The  adults  were  those  present 
when  the  fruit  had  been  stored,  and,  at  the  time,  were  probably  not 
very  fully  developed.  But  they  completed  their  development,  and  after 
an  interval  of  seven  months  young  were  still  appearing.  In  this  time 
the  fruit,  had  it  been  in  transit,  would  have  had  time  to  reach  most  any 
3— bul.  222 


128 


UNIVERSITY  OF  CALIFORNIA — EXPERIMENT  STATION. 


Fig.  19. — Tracings  showing  actual  movement  of  motile  young  red  scales  for 
a  two-hour  period.  Reduced  seven  times.  1  Temperature  66°  ;  average 
distance  traveled,  31  inches.  2  Temperature  91°  ;  average  distance  111 
inches. 


Bulletin  222]  THE  RED  OR  ORANGE  SCALE.  129 

part  of  the  world.  An  interesting  point  with  these  scales  was  that  they 
were  very  light  gray  or  grayish  white  in  color,  and  were  mistaken  at 
first  for  the  greedy  scale  (Aspidiotus  rapax) .  This  striking  difference 
in  color  from  the  usual  red  must  be  accounted  for  from  the  absence  of 
light,  since  they  were  securely  wrapped  in  paper  during  all  the  period. 

The  spread  of  the  red  scale  over  the  same  general  community  is 
effected  largely  by  birds  and  active  insects,  together  with  the  agency  of 
man  in  his  usual  cultural  operations.  In  the  spread  from  tree  to  tree, 
aside  from  the  above  factors,  the  power  of  the  insect  to  transport  itself 
is  entitled  to  consideration. 

Rate  of  travel  over  smooth  surfaces.  With  a  view  to  determining 
how  far  a  red  scale  would  travel  under  the  most  favorable  conditions, 
records  were  made  for  two  hour  periods  on  smooth  paper.  When  the 
temperature  was  66  °F.  four  active  young  red  scales  traveled  23,  25.5, 
34,  and  41  inches,  respectively,  or  an  average  of  31.12  inches.  Under 
the  same  conditions,  when  the  temperature  was  91°F.,  the  maximum 
distance  traveled  was  111  inches,  or  more  than  three  times  the  distance. 
Several  other  experiments  on  the  rate  of  travel  over  paper  showed 
similar  results. 

A  young  red  scale  is  active  for  from  twenty-four  hours  to  two  or  three 
days.  Very  rarely  have  they  not  settled  within  one  or  two  days.  But 
taking  the  maximum  period  of  activity,  under  conditions  where  no  food 
is  available  at  four  days,  the  total  distance  traveled  might  be  444  feet. 
This  is  on  the  basis  that  they  would  travel  55.5  inches  per  hour,  and 
keep  it  up  continuously  for  four  days.  This  distance,  of  course,  would 
never  be  approached  under  actual  conditions.  Two  active  young  were 
liberated  on  an  ordinary  picking  box,  and  one  crawled  eleven  inches 
and  the  other  six  inches  in  one  hour.  The  temperature  was  80°  F.  This 
test  was  duplicated  with  a  temperature  of  96°  F.,  and  the  longest  dis- 
tance covered  in  one  hour  was  eleven  inches,  and  the  shortest  distance 
eight  inches.  We  have  not  yet  succeeded  in  getting  the  young  red  scale 
to  live  more  than  four  days  without  food.  Picking  boxes,  gloves,  ladders; 
etc.  would  therefore  be  safe  to  take  into  a  clean  grove  without  fear  of 
infestation  through  these  things  after  a  period  of  four  or  five  days,  or, 
to  be  surely  on  the  safe  side,  one  week. 


130 


UNIVERSITY  OF   CALIFORNIA EXPERIMENT   STATION. 


Bate  of  travel  over  sand  and  orchard  soil.  A  number  of  experiments 
were  made  on  the  rate  of  travel  of  the  young  insects  over  sand  and 
orchard  soil.     Some  of  these  are  tabulated  below: 


Date. 

Tempera- 
ture. 

Number 

insects. 

Kind  of  soil. 

Radius 

of  soil.            Time. 

Results. 

July    15 

July   15 

90°F. 

90 

90 

88 

85 

85 

85 

89 

93 

82 

63 

78 

78 

76 

15 
15 
15 

20 
20 
20 
20 
15 
20 
20 
10 
20 
25 
20 
18 
18 
12 
12 
2 
2 

Sand 

Sand 

Sand 

Sand 

Orchard-soil 

Orchard-soil 

Orchard-soil 

Orchard-soil 

Orchard-soil 

Orchard-soil 

Orchard-soil 

Orchard-soil 

Orchard-soil 

Orchard-soil 

Sand 

Sand 

Sand 

Sand 

Compacted   silt 

Compacted  silt 

1  inch 
2£  inches 
3    inches 
21  inches 
21  inches 

2  inches 
2    inches 

2  inches 

3  inches 
3    inches 
3    inches 
3    inches 
3    inches 
3    inches 
21  inches 
21  inches 
2    inches 
1    inch 

5    inches 
5    inches 

4  hrs. 
4  hrs. 

4  hrs. 
17  hrs. 

17  hrs. 

5  hrs. 

14  hrs. 

18  hrs. 

15  hrs. 

19  hrs. 

19  hrs. 
24  hrs. 
24  hrs. 
24  hrs. 
24  hrs. 
24  hrs. 
24  hrs. 
24  hrs. 
30  min. 

20  min. 

0  crossed 

July  15 

0  crossed 

July   18 

1  crossed 

July  19  

0  crossed 

July   18 

July  18 

July   22  

July   20  

July   21 

July  23 

July   24 

July   25 

July   25 

Nov.  29 

0  crossed 
0  crossed 
0  crossed 
0  crossed 
2  crossed 
2  crossed 
2  crossed 
0  crossed 
0  crossed 
2  crossed 

Nov.  29 

1  crossed 

Nov.  26 

2  crossed 

Nov.  19 .__    

2  crossed 

July  18 

July   18  

88 
88 

2  crossed 
2  crossed 

From  the  above  experiments  it  will  be  seen  that  the  young  red  scale 
makes  very  little  progress  over  sand  or  ordinary  orchard  soil.  Out  of 
the  319  insects  tried  only  fourteen  crossed  over  the  strips  of  soil  indi- 
cated, which  did  not  exceed  three  inches  in  width.  None  of  them  suc- 
ceeded in  crossing  even  the  narrowest  strips  until  the  following  day.  In 
the  case  of  the  last  two  tests,  where  the  soil  was  compacted  in  an  irriga- 
tion furrow,  they  made  very  good  progress,  and  traveled  at  the  rate  of 
about  ten  inches  an  hour.  If,  then,  there  is  a  fairly  good  mulch,  as  is 
maintained  in  California  citrus  orchards  during  the  summer,  there  is 
little  chance  of  a  young  red  scale  ever  making  its  way  from  one  tree  to 
another  by  its  own  powers  of  locomotion.  But  during  the  winter  season 
when  the  surface  soil  is  compacted  by  rains,  or  through  irrigation  during 
the  summer,  there  may  be  some  possibility  of  this  occurring.  In  the 
case  of  the  mulch  the  young  scales,  in  attempting  to  ascend  a  small 
particle  of  earth,  fall  back  in  the  attempt  and  flounder  about  without 
making  very  much  progress. 

On  account  of  the  limited  powers  of  locomotion  of  the  insects  them- 
selves, their  spread  must  be  accounted  for  through  outside  agencies.  Of 
these,  active  insects  must  be  the  most  important.  Among  the  insects 
responsible  for  their  spread,  those  which  are  to  be  found  crawling  about 
on  the  tree  where  the  scales  are  are  most  important.  Coccinelids  are, 
therefore,  entitled  to  first  consideration.  These  may  be  feeding  on  the 
scales  themselves,  and  thus  allow  abundant  opportunity  for  the  young 
scales  to  crawl  upon  them.    Indeed,  it  has  not  been  uncommon  to  actually 


Bulletin  222] 


THE  RED  OR  ORANGE  SCALE. 


131 


observe  many  of  the  beetles  carrying  young  scales  on  their  bodies  in  the 
insectary  and  also  in  the  field.  Others,  such  as  lace  wing  flies,  Dia- 
brotica,  and  ants  are  likely  to  aid  in  the  spread  of  young  scale  insects. 
The  tvind  is  hardly  as  important  as  popularly  believed  in  aiding  the 
spread  of  scales.  Of  course  the  adult  male  may  be  carried  some  distance 
by  the  wind,  but  the  active  young  are  too  heavy  for  their  size  to  be 
transported  very  far.  They  are  not  easily  dislodged  from  the  tree  by 
the  wind,  but  once  dislodged  may  be  carried  a  short  distance  while  they 
are  falling,  if  the  wind  is  sufficiently  strong.  But  the  wind  is  likely  to 
be  more  important  in  distributing  infested  leaves  about.  Here,  again, 
it  is  the  dead  leaves  that  are  conveyed  most  easily,  and  these  are  not  so 
likely  to  have  live  scales  as  the  green  or  yellowed  ones. 


Fig.  20. — Aphelinus  diaspidis.     1  Egg.     xl5.     2  Larva.     x65.     3  Head  segment 
showing  mandibles.     4  Pupa.     x60. 


PARASITES. 

Aphelinus  diaspidis  Howard. 
The  most  common  parasite  of  the  red  scale  at  the  present  time  is 
Aphelinus  diaspidis  Howard.    Indeed,  in  the  examination  of  red  scales 
from    many    parts 

of  the   citrus   belt  <-~-E^ypn3^ 

during  the  past 
three  years  this  has 
been  practically 
the  only  one  met 
with  in  any  num- 
bers. In  the  liter- 
ature that  has  ap- 
peared, and  ad- 
dresses made  in 
this  state  on  par- 

ooi+r.0    +liic  „„„+;„,,  Fig.  21. — Aphelinus  diaspidis  How.     Parasite  on  Red  and 

asites,  ims  parilCU-  Yellow  Scales.    x39. 


132  UNIVERSITY  OP  CALIFORNIA — EXPERIMENT  STATION. 

lar  insect  has  not  been  mentioned  in  connection  with  the  red  scale. 
It  may  be  possible  that  it  has  recently  become  prominent,  or  that  it  was 
considered  under  another  name.  It  is  true  that  the  parasites  of  the  red 
scale  have  received  less  attention  than  those  of  some  of  the  other  scales. 
That  it  has  become  abundant  rather  recently  is  not  impossible.  A. 
diaspidis  was  first  described  by  Dr.  L.  0.  Howard  in  1880  from  speci- 
mens bred  from  Aulacaspis  rosce  from  Florida.  Specimens  from  the 
same  scale  were  also  collected  at  Santa  Barbara,  California,  about  the 
same  time.  It  has,  therefore,  been  known  from  this  State  for  thirty 
years.  This  parasite  has  also  been  bred  from  a  species  of  Mytalispidis 
from  Japan  and  from  Aspidiotus  juglans  regia,  or  the  walnut  scale. 

It  has  been  usual  here  to  speak  of  such  a  parasite  as  this  of  the  red 
scale  as  an  internal  parasite,  but  this  is  not  strictly  true,  for  at  no  stage 
of  its  life  cycle  is  it  within  the  insect.  It  is  true  that  all  of  its  life, 
excepting  as  an  adult,  is  spent  beneath  the  scale  covering,  but  it  is 
always  outside  the  insect  itself.  The  egg  is  deposited  outside  of  the 
insect,  and  upon  hatching  the  larva  attaches  itself  to  the  body  and  sucks 
out  the  juices.  In  the  case  of  the  yellow  scale  parasite  Aspidiotiphagus 
citrinus,  which  also  attacks  the  red,  it  lives  within  the  body  of  the  insect 
and  is  strictly  an  internal  parasite.  Coccophagus  lecanii  and  Aphycus 
flavus,  parasites  of  the  soft  brown  scale  {Coccus  hesperidum)  are  also 
strictly  internal  parasites;  that  is,  they  live  within  the  body  of  the 
insect  and  entirely  surrounded  by  the  body  tissues  from  which  their 
food  supply  is  derived. 

ECONOMIC  VALUE. 

While  it  is  not  uncommon  to  find  this  parasite  on  red  scale  from  many 
sections  of  the  citrus  belt,  it  has  never  been  seen  occurring  in  large 
numbers.  Examination  and  counts  have  been  made  at  various  times 
during  the  past  three  seasons,  and,  thus  far,  we  have  not  found  the 
number  of  scales  parasitized  to  exceed  10  per  cent.  This  amount  of 
parasitization  is,  of  course,  of  little  value  in  checking  the  number  of 
scales.  The  parasite  was  usually  found  most  abundant  where  the  scales 
were  most  numerous. 

DESCRIPTION  OF  THE  STAGES. 

The  egg  is  yellowish  white  in  color,  ovate  in  form,  measuring  .16  mm. 
long  and  .96  mm.  wide.  There  is  a  conspicuous  micropyle  projecting 
from  the  narrower  end  and  also  attached  to  this  a  short  stalk  that  is 
doubled  back  on  itself.  The  chorion  is  smooth,  with  spherical  granular 
bodies  showing  through  with  transmitted  light. 

The  larva  when  full  grown  appears  as  a  more  or  less  structureless  top- 
shaped  globule,  measuring,  when  segments  are  normally  extended, 
.75  mm.  long  and  .5  mm.  wide.    It  tapers  considerably  more  toward  the 


Bulletin  222]  THE  RED  0R  ORANGE  SCALE.  133 

posterior  end,  and  there  is  a  slight  difference  between  the  dorsal  and 
ventral  surfaces.  The  distance  between  the  upper  and  lower  surfaces  is 
a  little  less  than  the  width  of  the  body  so  that  there  is  some  indication 
of  flatness.  The  color  is  glassy  white,  with  the  food  in  the  digestive 
tract  showing  distinctly  yellow,  oval  in  shape,  and  measuring  about  one 
half  the  dimensions  of  the  larva  itself.  There  are  thirteen  indistinct 
segments,  not  including  the  button  at  the  tip.  The  head  end  is  broadly 
rounded,  with  the  first  segment  disc-shaped  and  firmer  than  the  others, 
with  the  small  mouth  opening  in  the  center.  This  mouth  opening  is 
about  .20  mm.  in  diameter,  and  there  are  two  chitinous  spines,  man- 
dibles, projecting  toward  its  center  in  front.  These  spines  are  .18  mm. 
in  length  and  .15  mm.  wide  at  the  base  where  the  muscle  attachment 
occurs.  From  near  the  base  they  suddenly  narrow  into  a  sharp  pointed 
spine  which  is  chitinous  at  tip  and  brown  in  color.  These  are  used  for 
piercing  the  outer  wall  of  the  scale  and  for  holding  it  in  place  while  the 
fluids  are  sucked  from  the  body. 

The  pupa  is  dark  yellow  in  color,  with  ocelli  and  eyes  reddish  brown, 
and  a  similar  pigment  extending  around  the  anterior  margin,  and  to  a 
less  extent  about  the  posterior  margin  of  the  head.  Length  .75  mm., 
width  .375  mm.  The  adult  appendages,  enclosed  in  their  sheaths,  lie 
close  to  the  body  on  the  ventral  side.  Always  accompanying  the  pupa 
are  from  six  to  ten  black  or  dark  brown  torpedo  like  bodies  .125  mm. 
long  and  .055  mm.  broad,  which  are  evacuations  from  the  digestive  tract 
and  are  expelled  by  the  larva  preliminary  to  pupation. 

The  adult.  Length  .78  mm.,  wing  expanse  1.9  mm.,  general  color 
yellow,  eyes  black,  ocelli  dark  red,  antennae  dusky  and  darker  at  tip. 
The  eyes  are  not  covered  with  hairs.  The  antennae  are  six  jointed,  the 
club  being  about  three  times  the  length  of  the  penultimate  point.  The 
fringe  of  the  wings  is  narrow. 

LIFE  HISTORY  AND  HABITS. 

The  duration  of  the  egg  stage  is  from  four  to  five  days,  of  the  larval 
stage  twelve  to  sixteen  days,  and  of  the  pupal  stage  eight  to  ten  days. 
The  adult,  under  nearly  normal  conditions,  usually  died  in  four  or  five 
days. 

This  parasite  does  not  always  emerge  through  an  exit  hole  in  the  scale, 
but  very  commonly  simply  pushes  its  way  out  from  under  the  scale. 
The  scale  covering  seems  to  be  loosened  from  the  surface  in  most  cases 
so  that  this  means  of  emergence  is  comparatively  easy.  This  is  further 
brought  about  by  the  movement  of  the  parasite,  and  also  because  of  the 
fact  that  the  scale  covering  is  always  separated  from  the  insect  and  has 
a  chance  to  loosen  before  the  parasite  is  mature.  In  case,  however,  the 
scale  covering  is  held  securely  to  its  resting  surface  the  parasite  eats  out 
an  irregular  hole  in  the  scale  covering  just  beyond  the  molted  skin,  in 


134  UNIVERSITY  OF  CALIFORNIA — EXPERIMENT  STATION. 

the  case  of  female  scales,  and  at  the  posterior  third  in  the  case  of  male 
scales.  The  parasite  almost  invariably  is  lying  on  its  back  as  a  pupa. 
Not  infrequently  two  pupa?  are  found  under  one  scale,  and  one  case  has 
been  observed  where  there  were  three. 

The  egg  is  deposited  under  the  scale  covering,  but  either  on  the  upper 
or  lower  side  of  the  insect  itself,  most  commonly  on  the  lower.  It  is  not 
inserted  within  the  body  of  the  insect.  Preliminary  to  oviposition  a 
thorough  examination  is  made  of  the  scale  by  alternately  tapping  with 
the  antennas  from  the  center  of  the  scale  to  the  periphery.  Upon  reach- 
ing the  edge  of  the  scale  a  rapid  backward  movement  is  made,  at  the 
same  time  turning  slightly  around  so  that  the  entire  surface  is  explored 
by  the  antennae  in  from  five  to  eight  backward  and  forward  movements 
in  a  remarkably  short  time.  This  procedure  may  occur  with  but  one 
scale  before  the  ovipositor  is  inserted,  and  again  a  dozen  or  more  may 
be  gone  over  without  finding  a  suitable  scale  for  oviposition.  But  the 
parasite  does  not  rely  alone  on  the  exploration  with  the  antennae,  for 
the  ovipositor  may  be  inserted  many  times  without  any  eggs  being 
deposited.  Insertion  with  the  ovipositor  may  occur  with  the  insect 
beneath  in  various  conditions,  and  not  infrequently  it  is  dead  and 
shriveled  up.  But  exploration  by  the  ovipositor  is  the  final  reliance  for 
the  placing  of  the  egg. 

The  ovipositor  is  not  inserted  under  the  scale  covering,  but  through  it 
just  beyond  the  insect  beneath.  The  parasite  is  facing  away  from  the 
scale  during  oviposition  so  that  the  ovipositor  is  pushed  down  and  back- 
ward toward  the  center  of  the  scale. 

A  specific  case  will  serve  to  illustrate  the  behavior  during  oviposition. 
Parasite  inserted  ovipositor  and  laid  egg  in  scale  No.  1  occupying  five 
minutes.  One  insertion  was  made  in  each  of  three  other  scales  occupy- 
ing from  one  to  three  minutes  each.  No  eggs  deposited.  In  scale  No.  5 
ovipositor  inserted  eleven  times;  and  remaining  in  scale  as  follows: 
1  min. ;  f  min. ;  1  min. ;  If  min. ;  1  min. ;  1  min. ;  1J  min. ;  1  min. ;  f  min. ; 
1  \  min. ;  6f  min.  Scale  lifted  and  but  one  egg  deposited,  this  undoubt- 
edly at  last  insertion. 

Eggs  may  be  deposited  under  scales  of  various  stages  as  follows: 
Female  between  first  and  second  molt  and  between  second  molt  and  egg 
laying.  Male  after  first  molt,  propupa  and  pupa.  In  no  case  has  a 
larva  of  the  parasite  been  seen  with  a  scale  during  the  molting  periods 
or  during  the  egg-laying  period.  The  scale  during  these  periods  is  very 
different  than  at  other  times.  The  body  wall  is  hard  and  glassy,  while 
the  contents  are  more  fluid  and  the  insect  adheres  firmly  to  the  scale 
covering.  Between  the  molts  the  body  wall  is  flexible,  is  not  so  distended 
by  the  body  fluids,  and  the  scale  covering  very  readily  separates  from 
the  insect  itself.  This  last  point  accounts  for  the  readiness  with  which 
the  covering  is  lifted  in  many  cases  to  allow  the  escape  of  the  parasite. 


Bulletin  222]  THE  RED  0R  ORANGE  SCALE.  135 

The  fact  that  the  parasite  has  not  been  seen  infesting  a  scale  during 
the  molting  periods  or  the  egg-laying  stage  is  accounted  for  because  of 
the  checking  in  growth  of  the  scale.  So  far  as  our  observations  have 
gone,  eggs  are  not  deposited  under  scales  in  these  conditions.  The  effect 
of  the  parasite  on  the  host  seems  to  be  the  only  explanation  for  the  fact 
that  molting  may  not  occur  later,  and  before  the  parasite  has  developed. 
The  feeding  of  the  parasite  larva  seems  to  check  the  development  of 
the  scale  as  soon  as  it  is  attacked,  or  soon  thereafter. 

Some  of  the  Chalcid  parasites  have  been  recorded  as  feeding  at  the 
puncture  holes  made  by  the  ovipositor.1  This  has  not  been  observed  in 
the  case  of  A.  diaspidis.  Several  hundred  insertions  of  the  ovipositor 
have  been  watched  during  the  past  two  or  three  years,  so  that  such  a 
habit  can  not  be,  at  least,  counted  common.  The  egg  parasites  mentioned 
in  the  article  cited  would  be  able  to  get  the  drop  of  the  contents  which 
would  almost  certainly  be  exuded.  But  we  are  not  so  sure  that  any 
liquid  would  be  exuded  in  the  case  of  a  puncture  in  the  scale  covering  of 
some  of  the  armored  scales. 

This  would  be  possible  during  the  molting  periods,  or  the  egg-laying 
period,  when  the  body  is  well  distended  and  intimately  associated  with 
the  scale  covering.  But  A.  diaspidis  has  not  been  seen  to  oviposit  under 
such  scales.  And  at  other  times,  while  the  ovipositor  is  inserted  through 
the  scale  covering,  it  does  not  puncture  the  insect  itself,  or  if  it  does,  the 
liquid  would  be  apt  to  exude  underneath  the  covering  and  not  neces- 
sarily through  the  puncture  hole.  Such  a  habit  would  be  more  likely  to 
occur  with  those  parasites  that  deposit  their  eggs  within  the  body  of  the 
host,  instead  of  externally  as  diaspidis. 

Observations  have  been  made  on  this  species  feeding  on  a  droplet  of 
honey  dew  and  also  some  indication  that  they  feed  on  plant  tissue.  They 
have  been  observed  many  times  lying  prone  upon  the  surface  of  the 
fruit  or  leaf  working  the  mandibles  and  going  through  all  the  move- 
ments of  feeding.  But  no  feeding  scars  have  been  seen  with  the  lower 
power  lenses.  Coccophagus  lecanii  has  this  habit,  and  leaves  very  dis- 
tinct feeding  scars.  It  also  strokes  the  soft  brown  scales  to  secure  the 
drops  of  honeydew  similar  to  the  ants.  No  males  of  A.  diaspidis  have 
yet  been  seen,  although  a  large  number  of  specimens  have  been  collected 
from  various  places.  Parthenogenetic  reproduction,  therefore,  must  be 
the  usual  way.  An  isolated  female  that  had  emerged  was  immediately 
placed  in  a  glass  vial,  and  an  hour  or  two  later  deposited  an  egg  beneath 
a  scale  and  which  later  hatched. 

1Howard.     Jour.  Ec.  Entomology.     Vol.  3,  No.  3. 


136 


UNIVERSITY  OF   CALIFORNIA EXPERIMENT   STATION. 


Other  species  of  Hymenopterous  parasites  reared  from  the  red  and 
yellow  scales  in  California  are: 

Prospaltella  aurantii  Howard. 
Coccophagus  lunulatus  Howard. 
Aspidiotiphagus  citrinus  Craw. 
Signiphora  occidentalis  Howard. 
Aphycus  immaculatus  Howard. 
Alaptus  criococci  Girault. 

Physcus  flaviventris  How.,  has  been  reared  from  Chrysomphalus 
aurantii  Mask,  from  Manila,  P.  I. 


Key  to  the  Species  of  Parasites  Recorded  From  Chyrsomphalus  aurantii  and 

the  Variety  citrinus. 
Antennw  6-jointed. 

Wings  with  short  fringe,  Aphelinus  diaspidis. 

Wings  with  long  fringe,  Signiphora  occidentalis. 
Antennw  7-jointed. 

Physcus  flaviventris. 
Antennw  8-jointed. 

Stigmal  vein  lacking ;  fringe  long,  Aspidiotiphagus  citrinus. 

Stigmal  vein  present ;  fringe  short. 
Marginal  vein  as  long  or  longer  than  submarginal,  Coccophagus  lunulatus. 
Marginal  vein  much  shorter  than  submarginal,  Prospaltella  aurantii. 
Antennw  9-jointed. 

Aphycus  immaculatus. 
Antennw  of  female  8-jointed,  of  male  10-jointed. 

Alaptus  eriococci. 

Prospaltella  aurantii  Howard. 
This  species  was  originally  described  by  Dr.  Howard  in  Insect  Life, 
Vol.  VI,  p.  231,  in  1894.    The  specimens  were  reared  by  D.  W.  Coquillett 

from  Chrysomphalus  aurantii 
var.  citrinus  from  San  Gabriel, 
California,  in  1887.  The  origi- 
nal generic  name  was  given  as 
Coccophagus,  and  later  as  Pros- 
palta,  but  the  latter  was  pre- 
occupied so  that  the  genus  as  it 
now  stands  is  Prospaltella} 

This  parasite  is  not  common 

on  the  red  or  yellow  scales,  and 

It  is  also  recorded  from  Aspidiotus 

regia,    Lepidosaphes    beckii,    L.    alba, 


Fig. 


22. — Prospaltella  aurantii  How. 
After  Howard. 


x50. 


is  only  occasionally  met  with. 
ancylus,  A.  pini,  A.  juglans 
Eulecanium  persicw,  Chionaspis  sp.2 


Coccophagus  lunulatus  How. 
This  parasite  was  described  from  one  female  reared  from  Chrysom- 
phalus aurantii  from  Los  Angeles  in  1892.     Red  scale  infested  leaves 


toward.     Jour.  Ec.  Ent.     Vol.  4,  No.  1,  1911. 

2Howard.     Tech.  Series  I,  Bull.  U.  S.  D.  A.,  Bur.  Ent.,  1895. 

3Howard.     Insect  Life.     Vol.  VI,  p.  232. 


Bulletin  222] 


THE  RED  OR  ORANGE  SCALE. 


137 


were  placed  in  a  jar  and  a  week  later  the  above  parasite  issued.3  There 
is  some  doubt  in  the  writer's  mind  about  this  insect  being  reared  from 
the  red  scale.  Species  of  the  genus  Coccophagus,  with  this  single  excep- 
tion, do  not  attack  members  of  the  Diaspince  group.     The  size  of  the 


Fig.  23. — Coccophagus  lunulatus  How.     x50.     After  Howard. 

parasite  is  also  rather  large  to  mature  in  a  red  scale.  The  size  as  given 
in  the  original  description  is  .93  mm.,  while  the  average  dimensions  of 
the  mature  scale  are  .78  mm.  wide  and  1  mm.  long.  The  lengths  of  the 
other  parasites  of  this  same  host  are  .61  mm.,  .55  mm.,  .53  mm.,  .58  mm., 
and  .70  mm.  It  would  not  be  unlikely  that  it  issued  from  Coccus  hes- 
peridum,  which  are  so  frequently  found  on  the  orange  leaves. 

Aspidiotiphagus  citrinus  Craw. 
A  discussion  of  this  insect  will  be  found  under  the  head  of  "Yellow 
Scale  Parasites. " 

Signiphora  occidentalis  How. 
This  insect  was  described 
by  Dr.  Howard  from  mate- 
rial reared  from  Chrysom- 
phalus  aurantii  var.  cit- 
rinus, from  San  Gabriel, 
California.  It  has  also 
been  taken  from  Lepido- 
sophes  gloverii,  Aspidiotus 
cydonice  and  Aleyrodes  sp. 
The  original  description 
is  given  in  Insect  Life, 
Vol.  VI,  p.  235. 


Fig.  24. — Signiphora  occidentalis  How. 
After  Howard. 


x50. 


138 


UNIVERSITY  OF   CALIFORNIA — EXPERIMENT  STATION. 


Aphycus  immaculatus  How. 
This  species  has  been  reared  by  D.  W.  Coquillett  from  Chrysomphalus 
aurantii  from  Los  Angeles,   California,  and  described  by  Dr.  L.   0. 
Howard  in  Insect  Life,  Vol.  VI,  p.  236.     It  has  not  been  observed  by  us 
daring  the  past  three  years. 


Fig.    25. — Aphycus  immaculatus   How.      x50. 
After  Howard. 

Alaptus  eriococci  Girault. 
This  species  has  been  reared  from  Chrysomphalus  aurantii  and  Bhi- 
zoccus  araucarice  from  Los  Angeles,  and  described  by  Mr.  A.  A.  Girault 
in  the  Annals  of  the  Ent.  Soc.  of  America,  Vol.  I,  No.  3,  1908. 


*-> 


Fig.   26. — Aphelinus  sp.     Larva,  pupa,  adult.      Reared  from  Aspidiotus  hederae  Vail. 


PREDATORY  ENEMIES. 
Ehizooius  lopanthce.  Blaisd. 
This  Coccinelid  is  probably  the  commonest  and  most  abundant  one 
feeding  upon  the  red  scale.  While  it  is  not  restricted  in  its  feeding  to 
this  scale  exclusively  it  has  been  found  more  often  associated  with  it 
than  any  of  the  other  scales,  unless  it  be  the  purple.  It  has  been  called 
the  "Purple  Scale  Rhizobius,"  but  this  name  is  no  more  justifiable  than 


Bulletin  222] 


THE  RED  OR  ORANGE  SCALE. 


139 


"Red  Scale  Rhizobius."  In  fact,  the  latter  would  be  an  appropriate 
common  name  just  as  the  "Black  Scale  Rhizobius"  would  be  similarly 
appropriate  for  Rhizobius  ventralis.  Where  both  the  red  and  black 
scales  occur  in  the  same  orchard,  or  even  on  the  same  tree,  ventralis  will 
be  found  with  the  black  and  lophanthce  with  the  red. 


Fig.  27. — Prospaltella    sp.      Internal    parasite    from 
Aspidiotus  hederae  Vail. 

The  eggs  of  B.  lophanthce  are  often  found  beneath  the  red  scale. 
Usually  but  one  or  two  are  found  under  the  same  scale.  They  are  small 
oval  shaped  eggs  white  in  color  with  a  metallic  iridescence.  Upon 
hatching  the  larva  makes  its  way  from  beneath  the  scale,  consuming  first 
the  scale  under  which  it  is  found,  if  it  offers  suitable  food,  and  later 
attacks  many  different  scales  before  reaching  maturity.  It  eats  out  an 
irregular  hole,  rectangular  usually,  in  the  scale  covering  and  most  com- 
monly just  beyond  the  insect  which  is  lying  beneath. 


— Rhizobius   lopanthae  Blaisd. 
and  pupa,  xlO  ;  and  adult,  x5. 


Larva 


The  mature  larva  is  4  mm.  in  length  and  about  1  mm.  wide.  The 
general  color  is  dark  gray  with  a  lighter  rectangular  area  on  dorsal  line 
of  first  four  abdominal  segments.  There  is  also  a  strip  similar  in  color 
on  either  side  of  the  dorsal  line  on  the  meso-  and  meta-thoracic  segments, 
also  two  narrower  strips  more  laterally  on  last  four  abdominal  segments. 


140 


UNIVERSITY  OP  CALIFORNIA — EXPERIMENT   STATION. 


There  is  a  double  row  of  conspicuous  papillae  from  each  of  which  arise 
two  or  three  hairs,  the  central  papilla  and  hairs  being  longest.  The 
hairs  are  light  colored.  There  is  a  row  of  very  small  inconspicuous 
hairs,  two  on  each  segment,  on  either  side  of  the  dorsal  line. 

The  adult  is  a  small  beetle,  measuring  2  to  2-J  mm.  in  length.  The 
elytra  are  metallic  black  in  color  and  covered  with  grayish  or  light 
brown  hairs.  The  pro-thorax  is  brown  with  a  faint  darker  band  extend- 
ing horizontally  across  the  middle.  Eyes  black.  Ventral  surface  and 
legs  brown.     This  is  sometimes  called  the  "little  brown  neck  beetle" 


Fig.   29. — Some  common  ladybird  beetles  that   feed  on   the   Red   Scale. 

1.  Scymnus  marginicollis,  Mann. 

2.  Rhizobius  lophanthae,  Blaisd. 

3.  Scymnus  nebulosis,  Lee. 

4.  Hippodamia  convergens,  Guer. 

5.  Coccinella  californica,  Mann. 

6.  Hippodamia  ambigua,  Lee. 

7.  Hippodamia  ambigua,  Lee. 


x5. 


Bulletin  222]  THE  RED  OR  ORANGE  SCALE.  141 

because  of  the  color  of  its  pro-thorax,  but  others  nearly  similar  in  size 
and  appearance  might  be  confused  with  it. 

Besides  the  red  scale,  this  beetle  is  known  to  attack  the  yellow 
(C.  aurantii  var.  citrinus)  the  oleander  (Aspidiotus  hederce)  the  greedy 
(A.  rapax)  and  the  purple  (L.  beckii).  It  has  been  found  commonly 
feeding  on  the  purple  scale,  both  in  the  vicinity  of  Los  Angeles  and  San 
Diego.  Its  attacks  on  the  purple  appear  to  be  limited  more  to  the 
young  or  partly  grown.  The  mature  purple  with  its  firm  covering  seems 
to  be  better  protected  from  its  attacks. 

THE  STEEL-BLUE  LADYBIRD  BEETLE. 

Orchus  chalybeus.  Boisd. 
This  beetle  is  most  abundant  in  Santa  Barbara  County.  It  is  found 
well  distributed  over  the  citrus  section  of  that  county,  and  often  occurs 
in  large  numbers.  It  is  said  to  feed  especially  on  the  red  and  yellow 
scales.  But  it  is  not  limited  to  those  scales,  and  where  it  was  seen  most 
abundantly  in  Santa  Barbara  County  it  was  associated  with  the  black 
scale. 

OTHER  ENEMIES. 

There  are  many  other  Coccinellids  which  may  feed  on  the  red  scale 
occasionally,  but  these  are  still  more  general  in  their  feeding  than  the 
two  mentioned.  Our  commonest  native  species  including  Hippodamia 
convergens,  Coccinella  calif ornica,  Chilocorus  livulnerus,  and  others  are 
all  very  general  feeders  and  no  one  of  them  is  particularly  effective  as 
a  check  on  the  scale.  Aside  from  the  Coccinellidce,  other  enemies  are 
certain  species  of  the  families  Chrysopidce,  HemeroliidcB,  and  Reduviidaz, 
and  the  predaceous  mites. 

THE  YELLOW  SCALE. 

{Chrysomphalus  aurantii  var.  citrinus  Coq.) 
This  scale  is  very  similar  to  the  red  (C.  aurantii),  and  is  classified  as 
a  variety  having  the  varietal  name  citrinus.  It  is  widely  distributed 
over  the  citrus  belt  of  southern  California,  often  associated  more  or  less 
with  aurantii.  But  in  addition  to  its  occurrence  in  the  southern  part  of 
the  state  it  is  also  found  on  the  citrus  trees  of  the  Sacramento  Valley. 
There  it  is  the  most  important  scale  occurring  on  citrus  trees.  In  the 
same  section  the  typical  aurantii  is  not  known.  Why  it  doesn't  occur 
there  is  not  satisfactorily  accounted  for.  In  the  interchange  of  nursery 
stock  aurantii  has  probably  had  abundant  opportunity  of  becoming 
established  in  the  section.  In  fact,  it  is  more  likely  to  have  been  intro- 
duced, because  of  its  wider  occurrence  in  the  south  than  citrinus.  But 
it  is  not  altogether  improbable  that  the  variety  has  predominated  and 
become  established.  Experiments  are  now  under  way  with  a  view  to 
determining  the  factors  responsible  for  such  a  distribution. 


U2 


UNIVERSITY  OF   CALIFORNIA EXPERIMENT   STATION. 


In  the  citrus  belt  of  the  south  the  yellow  occurs  in  various  degrees  of 
severity  ranging  from  occasional  scales  scattered  about  on  parts  of  the 
tree,  to  badly  infested  trees  requiring  treatment.  In  Santa  Barbara 
County  at  the  present  time  the  yellow  is  more  common  than  the  red.  In 
San  Bernardino  and  Riverside  counties  the  yellow  ranks  second  in 
importance  among  the  insects  of  citrus  trees,  the  red  holding  first  place. 
In  Los  Angeles,  Orange  and  San  Diego  counties  the  yellow  is  not 
counted  among  the  first  three.  In  these  counties,  to  be  sure,  its  place 
may  be  pre-empted  by  the  purple.  In  former  years  it  is  said  to  have 
occurred  in  great  abundance  in  certain  sections  as  San  Gabriel  in  Los 
Angeles  County. 


pimi  ■■■- 

-•,•■"•• 

Fig.  30. — Yellow  Scale,  chrysomphalus  aurantii  var.  citrinus, 
on  orange. 

Economic  importance.  While  the  yellow  scale  may  frequently  become 
abundant  to  the  extent  of  injuring  the  tree,  it  can  not  be  counted  as 
serious  as  the  red.  This  is  partly  because  of  its  well  known  habit  of 
avoiding  the  twigs  and  branches,  and  infesting  largely  the  fruit  and 
foliage.  The  yellow  is  found  on  the  branches  to  some  extent,  but  usually 
only  in  severe  infestations,  and  even  then  only  scattering.  Trees  have 
been  seen  where  the  leaves  and  fruit  were  completely  covered  with  yellow 
scale  for  two  or  three  years  in  succession,  yet  the  tree  itself  was  not 
seriously  damaged.  Of  course,  with  such  an  infestation  the  tree  is 
injured  because  of  the  injury  to  the  leaves,  and  the  fruit  is  rendered 
unfit  for  market.  But,  if  a  similar  infestation  had  occurred  with  the 
red,  a  large  portion  of  the  tree  would  have  been  killed  outright. 

Another  point  that  makes  the  yellow  less  to  be  feared  in  many  sec- 


Bulletin  222] 


THE   RED   OR   ORANGE   SCALE. 


143 


Fig.  31. — Yellow  Scale  on  orange  leaf;  upper  surface. 


Fig.  32. — Yellow  Scale  on  under  side  of  same  leaf  as 
shown  in  Fig.   33. 


4— bul.  222 


144 


UNIVERSITY   OF   CALIFORNIA EXPERIMENT   STATION. 


tions  is  its  apparent  lack  of  vigor,  either  of  breeding  or  of  becoming 
established  rapidly.  Exceptions  may  occur  to  this  statement,  as  they 
do  in  the  north  and  also  in  cases  in  the  south.  But  it  is  not  uncommon 
to  find  scattering  infestations  of  yellow  in  a  grove  for  years  without 
becoming  abundant  enough  to  attract  attention  or  make  it  worth  while 
inaugurating  control  measures.  Here  is  the  opportune  point  to  give 
credit  to  the  parasites.  But  in  those  cases  under  consideration  there 
were  less  parasites  than  on  the  red,  and  this  maximum  was  only  10  per 
cent. 

Differences  between  the  red  and  yellow  scales.  Structurally  there  are 
do  differences,  thus  far  discovered  in  the  insect  itself,  between  the 

species  aurantii  and  its  variety  cit- 
rinus.  Exactly  the  same  morpholog- 
ical characters  occur  in  both,  so  that 
under  the  microscope  it  is  not  possible 
to  be  sure  whether  it  is  the  red  or  yel- 
low that  is  being  examined.  But  the 
difference  in  appearance  as  they  are 
found  on  the  tree  is  usually  not  diffi- 
cult to  determine.  The  yellow  is  much 
lighter  in  color,  is  often  less  convex 
and  often  appears  slightly  larger  in 
diameter.  The  additional  fact  that 
they  are  not  found  to  any  extent  on 
the  twigs,  makes  the  field  determina- 
tion easy  enough.  But  if  only  a  few 
specimens  are  seen  on  a  leaf,  and  these 
fig.  33. — Yellow  Scale  showing  exit    are  not  typically  red  or  yellow,  the 

hole    of    Asiridiotiphagus    citrinus.  . 

Mouth    parts    of    scale    showing    determination   is   difficult    and   often 
below  in  opening,    xioo.  impossible.     This  is  particularly  true 

of  old,  dead  scales  which  in  the  case  of  the  yellow  become  much  darker  in 
color  and  makes  the  similarity  more  complete. 

The  difference  in  color  is  not  due  to  the  insect  itself  so  much  as  in 
the  scale  covering.  When  the  insects  are  free  from  the  scale  covering, 
as  between  the  molts,  it  is  often  very  difficult  to  distinguish  the  red  from 
the  yellow,  though  before  the  same  scales  were  lifted,  the  difference  may 
have  been  evident  enough.  But  during  the  molting  periods  the  red  is 
much  darker  in  color  than  the  yellow.  Since  the  dorsal  half  of  the 
cast  skin  is  incorporated  into  the  scale  this  difference  persists  in  the 
scale  covering.  The  color  of  the  insects  is  most  usually  a  light  yellow, 
both  with  the  red  and  yellow.  But  there  is  considerable  variation,  and 
the  red  is  often  apt  to  be  distinctly  darker  in  color,  this  being  most 
marked,  as  intimated  during  the  molting  period  or  during  the  produc- 
tion of  young. 


Bulletin  222] 


THE  RED  OR  ORANGE   SCALE. 


145 


Aside  from  the  difference  in  habits  of  the  two  scales  in  attacking  the 
twigs,  there  are  other  differences  in  habits.  Where  there  are  but  a  few 
scattering  scales  the  yellow  will  be  most  likely  to  occur  on  the  lower 
side  of  the  leaves  and  usually  too  on  those  leaves  near  the  lower  part  of 
the  tree.  In  severe  infestations  also  the  lower  side  of  the  leaves  are 
likely  to  have  the  greatest  number  of  scales.  Of  course  the  red  will 
often  be  found  on  the  under  side  of  the  leaves  as  well  as  the  upper,  but 
the  habit  the  yellow  has  sometimes  of  settling  entirely  on  the  lower  side 
is  not  so  true.  The  red  is  not  averse  to  getting  into  the  light  and  more 
open  parts  of  the  tree,  while  in  many  cases  the  yellow  has  the  opposite 
habit.  Where  the  occurrence  of  the  yellow  is  severe,  all  parts  of  the  tree 
may  be  attacked.  But  it  can  not  be  said  that  the  yellow  doesn't  like 
heat,  for  it  is  most  important  in  the  warmest  part  of  the  southern  citrus 
belt,  and  occurs  exclusively  in  the  large  interior  valleys  of  the  north, 
where  the  summers  are  hotter  than  any  part  of  the  southern  belt. 

The  life  history  of  the  yellow  has  been  found  to  agree  in  all  essential 
particulars  with  that  of  the  red.  The  discussion  of  the  seasonal  history, 
locomotion,  and  spread  also  corresponds  in  both,  so  that  these  topics 
will  not  be  again  considered. 


PARASITES. 

Aspidiotiphagus  citrinus  Craw. 
While  the  same  parasite  is  likely  to  attack  either  the  red  or  yellow,  it 
being  unlikely  that  it  is  able  to  distinguish  the  varietal  differences,  yet 
our  acquaintance  thus  far  with  the  following  parasite  has  been  largely 
in  connection  with  the  yellow. 
This   is   Aspidiotiphagus   cit-  i 
rinus  Craw,  formerly  known 
in  this  state  as  the  "golden 
chalcid. "      It   has   been   met 
with  most  commonly  in  Santa 
Barbara  County.     That  it  oc- 
curs here  on  the  yellow  may 
be  accounted  for  because  of 
the  fact  that  the  yellow  is  the 
commonest  of  the  two  scales 
that     county.      However, 


in 

some  red  were  obtained  in  one 
of  the  localities  where  the  yel- 
low occurred,  but  we  did  not 
happen  to  secure  any  of  the 
parasites  from  this  material. 
This  parasite  was  only  rarely  obtained  during  the  past  three  years  from 
either  red  or  yellow  scale  material  obtained  from  about  Whittier,  Los 


'"^VAA 


Fig 


34. — Aspidiotiphagus  citrinus.  1  Egg.  xl75. 
2  Larva.  x30.  3  Yellow  Scale  harboring 
larva.      4   Pupa.      x65. 


146 


UNIVERSITY  OP   CALIFORNIA EXPERIMENT   STATION. 


Angeles,  Pomona,  Redlands,  Riverside,  Santa  Ana,  and  San  Diego.  It 
was  found  more  abundantly  at  Marysville,  Oroville,  Chico,  Sacramento 
and  Santa  Barbara.  Indeed,  in  the  Sacramento  Valley  section  is  where 
the  heaviest  parasitization  has  been  noted.  Counts  on  a  large  number 
of  scales  from  that  section  showed  the  percentage  of  parasitization  to 
run  as  high  as  67. 

Aspidiotiphagus  citrinus  has  been  taken  rather  abundantly  from 
purple  scale  in  certain  sections,  especially  where  fumigation  has  not  been 
regularly  practiced.  It,  therefore,  attacks  the  purple  scale  readily,  and 
is  not  limited  solely  to  the  yellow  as  is  supposed  by  some. 

The  egg  of  A.  citrinus  is  oval  in  general  shape,  but  distinctly  flattened 
on  one  side.  There  is  a  minute  stalk  at  one  end  and  the  egg  is  slightly 
more  tapering  at  this  end ;  color  transparent,  granular ;  length  .08  mm., 
width  .007  mm.  The  egg  is  found  within  the  body  of  the  scale.  The  one 
described  was  deposited  at  5  p.  m.  December  30,  1910,  and  was  dissected 
from  the  scale  and  examined  on  January  3,  1911. 

The  mature  larva  is  glassy  white  in  color;  length  .85  mm.  long  and 
.35  mm.  broad  at  widest  part,  which  is  about  the  middle.  It  is  thus  much 
more  elongate  than  that  of 
diaspidis.  The  segments  are 
very  indistinct.  While  the 
middle  is  slightly  widest,  the 
head  end  is  broad,  but  there 
is  a  gradual  tapering  to  a 
narrow  point  at  the  posterior 
end.  The  mouth  opening  is 
in  the  center  of  the  disc- 
shaped anterior  segment. 
The  mandibles  are  much  nar- 
rower at  the  base  than  those 
of  diaspidis.  This  character, 
together  with  the  difference  in  the  general  shape,  will  readily  distin- 
guish the  two  larvaa.  The  larva  of  Aspidiotiphagus  citrinus  lives 
strictly  within  the  body  of  the  insect  itself. 

The  pupa.  Length  .6  mm.,  width  .28  mm.  The  general  color  upon 
first  changing  from  the  larva  is  white  or  whitish  yellow,  but  it  later 
turns  very  much  darker.  The  head  is  light  gray  and  thorax  and  abdo- 
men almost  black,  with  the  abdominal  segments  lighter  in  color  at  the 
margins,  giving  a  horizontal  striped  effect.  The  eyes  and  ocelli  are  red 
or  reddish  brown. 

The  adidt.  General  color  yellowish  black.  Head  dull  yellow,  ocelli 
red,  eyes  black.  Thorax  dark  yellow,  with  darker  areas  about  bases  of 
wings.     Abdomen  black,  lighter  at  tip.     Legs  pale  colored.     Antennae 


Fig. 


35. — Aspidiotiphagus  citrinus  Craw. 
Parasite  of  Yellow  and  Red  Scales. 


x40. 


"Bulletin  222] 


THE  RED  OR  ORANGE   SCALE. 


147 


Fig.   36. — Fruit  showing  cells  for  rearing  parasites. 


Fig.  37. — Above,  cages  enclosing  small  orange  trees  for 
studying  parasites.  Below,  method  of  keeping  accu- 
rate records  on  life  history  of  scales. 


148  UNIVERSITY  OF   CALIFORNIA EXPERIMENT   STATION. 

8-jointed,  comparative  lengths  as  follows:  5,  25,  10,  8,  7,  10.  13.  18. 
Wings  narrow,  with  a  very  long  fringe ;  basal  half  dusky. 

Life  history  work  carried  on  with  this  parasite  during  the  winter 
months  indicates  that  67  or  68  days  are  necessary  for  the  complete  life 
cycle.  Adults  placed  in  cells  on  fruit  infested  with  scale  were  seen  to 
oviposit  in  the  scales  on  January  6th,  and  four  adults  issued  on  March 
14th  and  15th.  This  period  being  the  coldest  and  wettest  of  the  season 
must  account  for  the  slow  development.  During  September  the  life 
cycle  has  been  determined  to  occur  in  thirty  days.  The  scales  attacked, 
whether  they  be  yellow  or  purple,  are,  with  a  few  exceptions,  always 
in  the  second  stage,  that  is  between  the  first  and  second  molts. 


SYSTEMATIC  POSITION  OF  CHRYSOMPHALUS  AURANTII  MASK. 

The  family  Coccidce,  which  includes  the  scale  insects,  is  divided  into 
six  sub-families.  The  red  scale  belongs  to  the  sub-family  Diaspince, 
which  includes  all  those  scales  having  flattened  chitinous  lobes  at  the 
posterior  end  of  the  body  forming  the  pygidium.  The  genus  Chrysom- 
phalus  is  distinguished  by  having  three  distinct  pairs  of  these  lobes. 
There  are  in  California  but  three  species  and  one  variety  coming  within 
this  genus.  The  species  aonidium  is  separated  from  the  others  by  having 
four  groups  of  spinnerets.  The  others  have  no  groups  of  spinnerets.  In 
the  species  tenebricosus  the  plates  are  scarcely  branched,  while  in  the 
species  aurantii  and  the  variety  citrinns  the  plates  are  strongly 
branched. 

C.  aonidum,  formerly  known  as  ficus,  is  known  as  the  Florida  red 
scale.  It  is  not,  however,  as  serious  a  pest  there  as  our  red  scale  here. 
It  is  especially  likely  to  infest  plants  in  conservatories  or  under  glass. 
Its  occurrence  in  this  state  is  based  on  an  infestation  of  palms  in  a 
o'reenhouse. 


Bulletin  222]  THE  RED  0R  ORANGE  SCALE.  149 

BIBLIOGRAPHY. 

For  the  bibliography  of  Chrysomphalus  aurantii  up  to  1903,  the 
reader  is  referred  to  Mrs.  Fernald's  "Coccidee  of  the  World."  The 
following  is  the  bibliography  since  1903,  which  has  been  kindly  fur- 
nished by  Mr.  E.  R.  Saccer  of  the  Bureau  of  Entomology,  Washington: 

Chrysomphalus  aurantii  Mask. 

Ehrhorn,  E.  M. :  1st  Bien.  Rept.  Comm.  of  Hort.  Sta.  Cal.  1903-04,  pp.  112-113. 
Sanders:  Proc.  Ohio  Ac.  Sci.,  iv   (2).     Sp.  papers  8,  p.  71   (1904).     Figs.  15-16. 

Gives  bibliography  and  description. 
Hempel:  Bol.  Agr.  Sao  Paulo,  V,  p.  322  (1904). 

Describes  hosts,  etc. 
Trabut,  Dr.:  Bull.  Agr.  de  Alg.  et  del  Tunisie,  X,  No.  23,  p.  521   (1904). 

'Au  sujet  d'un  insecte  destructeur  de  l'oranges." 
Theobald:  2d  Rep.  Ec.  Ent.  Br.  Mus,  p.  187  (1904). 

Record  of  9s  only. 
Kirkaldy,  G.  W. :  The  Entomologist,  Vol.  XXXVII,  Sept.  1904,  p.  228. 
Cockerell,  T.  D.  A. :  Proc.  Davenport  Acad,  of  Sciences  Vol.  X,  p.  134.     1905. 
Dickel,  Dr.  O. :  Zeit.  f.  wiss.  Inskt  Heft  II  Bard  I,  Nov.  20,  1905,  p.  447. 
Dewar.  W.  R. :  1st  Ann.  Rep.  Gor.  Entom.,  Orange  River  Colony  (1905),  p.  30. 

"This  is  at  present  the  greatest  insect  enemy  of  citrus  trees  in  the  O.   R.   C." 

Orange  River  Colony. 
Leonardi,  G. :  Redia,  iii,  p.  1   (1906).     Fig. 

Described  as  Aonidiella  taxus,  but  appears  to  be  a  synonym  of  A.  aurantii. 
Newstead,  R.  :  The  Inst,  of  Commercial  Research  in  the  Tropics.     Liverpool  Univ. 
Quarterly  Jn.     Vol.  1,  No.  11,  April,  1906,  p.  69. 

Frequently  received  from  Egypt. 
Craw,  A. :  Rep.  Die.  Entom.,  Hawaii  Bd.  Ag.  &  Forestry,  Dec.  31,  '06,  pp.  143,  152. 

"Well  established  in  the  islands." 
Herrera,  A.  L. :  Bol.  d.  1.    Com.  de  Parasitologia  Agricola  Tomo  III,  Num.  I  (1906). 
Ehrhorn,  E.  M. :  2d  Bienl.  Rep.  Com.  of  Hort.   Sta.  of  Cal.,  1905-'06,  pp.  23,  25, 

and  224. 
Green.  E.  E. :  Trans.  Linn.  Soc.  of  London,  Vol.  XII,  pt.  2,  Dec.  1907,  p.  203. 

Recorded  from  Mauritius,  Ceylon,  India,  S.  Europe,  Syria,  Natal,  Cape  Colony, 

China,    Japan,    Australia,    New    Zealand,    Java,    New    Caledonia,    Samoa,    Fiji, 

Hawaiian  Islands,  W.  I.,  U.  S.  A. 
Kuwana.  S.  I. :  Bull.  Imp.  Cent.  Agr.  Exp.  Sta.,  Japan,  Oct.  1907,  p.  196. 

Bibliography  on  Podocarpus  chinensis,  Acacia,  orange  and  tea  plants. 
Carnes.  E.  K. :  2d  Bien.  Rep.  Com.  Hort.  Sta.  Cal.  1905-06  (1907),  pp.  214-210. 
Leonardi.  G. :  Estratto  dal  Boll,  del  Lab.  di  Zool.  generale  e  agraria  clella  R.  Scuola 
Sup.  d'Agric.  di  Portici,  24  Mar.  1907. 

Europe   (Greece,  Turkey,  Italy,   Spain),   Syria,  Natal,   Good  Hope,   Is.   Maurizin 

e  Ceylon,  China,  Japan,  Australia,  New  Zealand,  Samoa,  Is.  Fiji,  Hawaii,  West 

Indies  (N.  Y.,  Fla.,  Ohio,  Cal.).     Gives  15  figures  and  list  of  food  plants. 
Fuller.  C. :  The  Natal  Ag.  Jn.  &  Mining  Record,  vol.  X,  No.  9,  Sept.  27,  '07,  p.  103G. 

The  parasitic  fungus  Sphaerostilte  coccophila  is  effective  on  the  coast. 
Lindinger.  L. :  Der  Pflanze  Ratg.  fur  Tropical  Landwirthschaft  No.  23,  Dec.  21,  '07. 

Jahr  III,  p.  359. 
Draper,  W.  :  Notes  on  the  Injurious  Scale  Insects  and  Mealy  Bugs  of  Egypt  (Cairo), 
1907.  p.  8. 

Common  throughout  Egypt. 
Newman.  L.  .T.  :  Jn.  Dep.  Ag.  of  Western  Australia,  Vol.  XV,  pt.  12,  Dec.  '07,  p.  915. 

"This  is  beyond  question  the  most  serious  scale  pest  of  the  citrus  trees  in  this 

state,  and  also  of  many  other  garden  plants." 
Ehrhorn.  E.  M. :  2d  Bien.  Rep.  Com.  of  Hort.  Sta.  of  Cal.  1905-'06,  p.  23. 
Lea,  A.:  Insect  and  Fungus  Pests  of  Orchard  and  Farm    (3d  edition),  Tasmania. 
p.  64   (1908). 


150  UNIVERSITY  OF   CALIFORNIA — EXPERIMENT   STATION. 

Froggatt,  W.  W. :  The  Ag.  Gaz.  of  N.  S.  W.,  Sept.  1908,  vol.  XIX,  part  9,  p.  704. 

"Common  all  over  Cyprus  gardens,"  on  roses  and  wattles. 
Froggatt,  W.   W. :   The  Jn.  Dept.  Ag.  of  So.  Austr.,   Feb.   1909,   vol.   XII,   No.  7. 

p.  620. 
Cook,  A.  J.:  Off.  Rep.  34th  Fruit-Grow.  Con.  of  Cal.,  p.  50,  Sacramento  (1908). 
Leonardi,  G. :  Cherm.  Ital.  Fasc.  IV,  Portici,  1908. 

Newman,  L.  J. :  Jn.  Dept.  of  Ag.  W.  Australia,  Dec.  1908,  vol.  XVII,  p.  912. 
Day,  C.  A.:  Proc.  of  33d  Fruit-Grow.  Con.  of  Cal.,  p.  163.     Sacramento   (1908). 
Ehrhorn,  E.  M. :   Proc.  of  33d  Fruit-Grow.  Con.  of  Cal.,  pp.  147-159.   Sacramento 

(1908). 
Cook,  A.  J. :  Pomona  Jn.  of  Ent.,  vol.  I,  No.  1,  March,  1909,  pp.  14-21.  figs.  11-15. 
Severin,  H.  C.  and  H.  H.  P.:  Jn.  Econ.  Entom.,  vol.  II,  No.  4,  p.  298.     Aug.  1909. 
lvuwana,  S.  I.:  Jn.  N.  Y.  Ent.  Soc.  XVII,  4,  p.  160  (Dec.  1909). 

On  Ligustrum  japonicum,  Artocarpus  integrifolia.     Bonin  Island,  Japan. 
Carnes,  E.  K. :  3d  Bien.  Kept.  Com.  Hort.  Cal.,  p.  25   (1909). 
Dean,  Geo.  A. :  Trans.  Kans.  Acad,  of  Sciences,  XXII,  p.  274  (1909). 
Lefroy,  H.  Maxwell:  Indian  Insect  Life,  p.  761  (1909). 
Lefroy,  H.  Maxwell:  Indian  Insect  Life,  p.  756  (1909). 
Brick,  C. :  Sta.  fur  Pflanzenschutz  zu  Hamburg.     X,  p.  9   (1909). 

Only  locality  and  food  plants  given. 
Brick,  C. :  Sta.  fur  Pflanzenschutz  zu  Hamburg.    X,  p.  10  (1909). 

"Auf   Cycas    circinalis   aus    Sanisbar,    auf    Palme    aus   Java   auf    Orchidee    auc 

Singapore." 
Brick,  C.  Sta.  fur  Pflanzenschutz  zu  Hamburg.     XI,  p.  5   (1909). 


STATION    PUBLICATIONS    AVAILABLE    FOR    DISTRIBUTION. 


REPORTS. 

1896.  Report  of  the  Viticultural  Work  during  the  seasons  1887-93,  with  data  regard- 

ing the  Vintages  of  1894-95. 

1897.  Resistant  Vines,  their  Selection,  Adaptation,  and  Grafting.     Appendix  to  Viti- 

cultural Report  for  1896. 

1902.  Report  of  the  Agricultural  Experiment  Station  for  1898-1901. 

1903.  Report  of  the  Agricultural  Experiment  Station  for  1901-03. 

1904.  Twenty-second  Report  of  the  Agricultural  Experiment  Station  for  1903-04. 


BULLETINS. 


Reprint.  Endurance  of  Drought  in  Soils  of 

the  Arid  Region. 
No.   128.  Nature,  Value,  and  Utilization  of 

Alkali  Lands,  and  Tolerance  of 

Alkali.      (Revised  and  Reprint, 

1905.) 
133.  Tolerance    of   Alkali    by   Various 

Cultures. 
147.  Culture  Work  of  the  Sub-stations. 
149.  California  Sugar  Industry. 

151.  Arsenical   Insecticides. 

152.  Fumigation  Dosage. 

153.  Spraying  with  Distillates. 

159.  Contribution     to     the     Study     of 

Fermentation. 
162.  Commercial  Fertilizers.      (Dec.  1, 

1904.) 
165.  Asparagus    and    Asparagus    Rust 

in  California. 

167.  Manufacture    of    Dry    Wines    in 

Hot  Countries. 

168.  Observations  on   Some  Vine  Dis- 

eases in  Sonoma  County. 

169.  Tolerance  of  the  Sugar  Beet  for 

Alkali. 

Studies  in  Grasshopper  Control. 

Commercial  Fertilizers.  (June 
30,   1905.) 

Further  Experience  in  Asparagus 
Rust  Control. 

A  New  Wine-cooling  Machine. 

Sugar  Beets  in  the  San  Joaquin 
Valley. 

A  New  Method  of  Making  Dry 
Red  Wine. 

Mosquito  Control. 

Commercial  Fertilizers.  (June, 
1906.) 

Resistant  Vineyards. 

The  Selection  of  Seed-Wheat. 

Analysis  of  Paris  Green  and 
Lead  Arsenic.  Proposed  In- 
secticide Law. 

The  California  Tussock-moth. 

Report  of  the  Plant  Pathologist 
to  July  1,  1906. 

Report  of  Progress  in  Cereal 
Investigations. 

The  Oidium  of  the  Vine. 

Commercial    Fertilizers.       (Janu- 
ary,  1907.) 
88.  Lining  of  Ditches  and  Reservoirs 
to  Prevent  Seepage  and  Losses. 

5— BUL.  222 


170. 
171. 

172. 

174. 
176. 

177. 

178. 
179. 

180. 
181. 

182. 


183. 
184. 


185. 


186. 
187. 


No.   189. 

190. 
191. 
192. 

193. 


194. 


195. 
197. 


198. 
199. 
200. 

201. 

202. 

203. 

204. 

205. 

206. 

207. 
208. 
209. 
210. 

211. 

212. 
213. 
214. 
215. 

216. 


217. 
218. 
219. 

220. 


Commercial  Fertilizers.  (June, 
1907.) 

The  Brown  Rot  of  the  Lemon. 

California  Peach  Blight. 

Insects  Injurious  to  the  Vine  in 
California. 

The  Best  Wine  Grapes  for  Cali- 
fornia ;  Pruning  Young  Vines ; 
Pruning  the  Sultanina. 

Commercial  Fertilizers.  (Dec, 
1907.) 

The  California  Grape  Root-worm. 

Grape  Culture  in  California ;  Im- 
proved Methods  of  Wine-mak- 
ing ;  Yeast  from  California 
Grapes. 

The  Grape  Leaf-Hopper. 

Bovine  Tuberculosis. 

Gum  Diseases  of  Citrus  Trees  in 
California. 

Commercial  Fertilizers.  (June, 
1908.) 

Commercial  Fertilizers.  (Decem- 
ber, 1908.) 

Report  of  the  Plant  Pathologist 
to  July  1,  1909. 

The  Dairy  Cow's  Record  and  the 
Stable. 

Commercial  Fertilizers.  (Decem- 
ber,  1909.) 

Commercial  Fertilizers.  (June, 
1910.) 

The  Control  of  the  Argentine  Ant. 

The  Late  Blight  of  Celery. 

The  Cream  Supply. 

Imperial  Valley  Settlers'  Crop 
Manual. 

How  to  Increase  the  Yield  of 
Wheat  in  California. 

California  White  Wheats. 

The  Principles  of  Wine-Making. 

Citrus  Fruit  Insects. 

The  House  Fly  in  its  Relation  to 
Public  Health. 

A  Progress  Report  upon  Soil  and 
Climatic  Factors  Influencing 
the  Composition  of  Wheat. 

Honey  Plants  of  California. 

California  Plant  Diseases. 

Report  of  Live  Stock  Conditions 
in  Imperial  County,  California. 

Fumigation  Studies  No.  5  ;  Dos- 
age Tables. 


CIRCULARS. 


No. 


30. 

32. 
3  3. 

3  6. 

39. 

46. 

48. 

49. 
50. 


Texas  Fever. 

Contagious  Abortion  in  Cows. 

Remedies  for  Insects. 

Asparagus  Rust. 

Fumigation  Practice. 

Silk  Culture. 

Recent  Problems  in  Agriculture. 
What  a  University  Farm  is  For. 

Disinfection   of   Stables. 

Preliminary  Announcement  Con- 
cerning Instruction  in  Practical 
Agriculture  upon  the  University 
Farm,  Davis,  Cal. 

White  Fly  in  California. 

White  Fly  Eradication. 

Packing  Prunes  in  Cans.  Cane 
Sugar  vs.  Beet  Sugar. 

Analyses  of  Fertilizers  for  Con- 
sumers. 

Instruction  in  Practical  Agricul- 
ture at  the  University  Farm. 

Suggestions  for  Garden  Work  in 
California  Schools. 

Butter  Scoring  Contest,   1909. 

Insecticides. 

Fumigation  Scheduling. 


No.   52.   Information  for  Students  Concern- 
ing the   College   of   Agriculture. 

54.  Some     Creamery     Problems     and 

Tests. 

55.  Farmers'    Institutes    and    Univer- 

sity Extension  in  Agriculture. 
Experiments  with  Plants  and  Soils 

in  Laboratory,  Garden,  and  Field. 
Tree      Growing      in      the      Public 

Schools. 

60.  Butter  Scoring  Contest,   1910. 

61.  University  Farm  School. 

62.  The  School  Garden  in  the  Course 
of  Study. 

How     to     Make     an     Observation 

Hive. 
Announcement   of  Farmers'    Short 

Courses  for  1911. 
The  California  Insecticide  Law. 
Insecticides  and  Insect  Control. 
Development  of  Secondary  School 

Agriculture    in    California. 

68.  The  Prevention  of  Hog  Cholera. 

69.  The    Extermination    of    Morning- 
glory. 

70.  Observations   on   Status   of   Corn- 
growing  in  California. 


58. 


5  9. 


63. 

64. 

65. 
66. 
67. 


